Body Fluids & Blood Circulation

Topic: Circulatory System; Subtopic: Heart Disorders

Keyword Definitions:

• Oxygen supply: The delivery of oxygen to tissues through blood circulation.

• Heart muscles: Myocardium, responsible for contraction and pumping of blood.

• Acute chest pain: Sudden pain in chest often due to reduced blood flow to heart muscles.

• Angina pectoris: Chest pain due to insufficient oxygen supply to heart muscles.

• Cardiac arrest: Sudden stoppage of heart activity leading to loss of circulation.

• Heart failure: Condition where heart cannot pump sufficient blood to meet body’s needs.

• Coronary Heart Disease: Disease caused by blockage or narrowing of coronary arteries.

• Myocardial ischemia: Condition of reduced blood flow to heart muscle.

• Circulatory system: Network of heart, blood, and vessels transporting nutrients and oxygen.

• Symptom: A sign or indication of a disease or disorder.

• Disorder: Abnormality in structure or function of an organ.

Lead Question - 2022 (Abroad)

Inadequate supply of oxygen to heart muscles leads to a symptom of acute chest pain. This disorder of the circulatory system is identified as:

1. Angina pectoris

2. Cardiac arrest

3. Heart failure

4. Coronary Heart Disease

Explanation: Angina pectoris is caused by insufficient oxygen delivery to heart muscles, leading to acute chest pain. Unlike cardiac arrest, heart failure, or coronary heart disease, angina is a symptom indicating myocardial ischemia. Prompt recognition and management prevent progression to severe heart conditions. Correct answer: 1

1. SINGLE CORRECT ANSWER MCQ

Which artery is primarily responsible for supplying blood to the myocardium?

1. Carotid artery

2. Coronary artery

3. Aorta

4. Pulmonary artery

Explanation: Coronary arteries branch from the aorta and provide oxygen-rich blood to the myocardium. Blockage of these arteries can cause ischemia and angina pectoris. Carotid supplies the brain, aorta distributes blood systemically, and pulmonary artery carries deoxygenated blood to lungs. Correct answer: 2

2. SINGLE CORRECT ANSWER MCQ

A prolonged blockage of coronary arteries may result in:

1. Angina pectoris

2. Myocardial infarction

3. Arrhythmia

4. Hypertension

Explanation: Prolonged coronary blockage prevents blood flow, causing permanent death of heart tissue, termed myocardial infarction. Angina is temporary ischemia, arrhythmia is irregular rhythm, and hypertension is high blood pressure. Correct answer: 2

3. SINGLE CORRECT ANSWER MCQ

Which of the following can trigger angina?

1. Physical exertion

2. Rest

3. Sleeping

4. Digestion of food

Explanation: Physical exertion increases oxygen demand of myocardium, which may exceed supply during coronary artery narrowing, triggering angina. Rest or sleep reduces demand, and digestion has minor effect unless combined with exertion. Correct answer: 1

4. SINGLE CORRECT ANSWER MCQ

Nitroglycerin relieves angina by:

1. Increasing heart rate

2. Dilating coronary vessels

3. Constricting blood vessels

4. Decreasing oxygen content of blood

Explanation: Nitroglycerin is a vasodilator that dilates coronary vessels, improving oxygen supply to ischemic myocardium, thus relieving angina. It does not increase heart rate, constrict vessels, or reduce oxygen content. Correct answer: 2

5. SINGLE CORRECT ANSWER MCQ

Which symptom is typical of angina pectoris?

1. Sudden unconsciousness

2. Severe chest pain on exertion

3. Persistent cough

4. Lower limb swelling

Explanation: Angina pectoris presents as severe, transient chest pain on exertion due to myocardial ischemia. Sudden unconsciousness may occur in cardiac arrest, cough is respiratory, swelling indicates heart failure. Correct answer: 2

6. SINGLE CORRECT ANSWER MCQ

Primary cause of angina is:

1. Myocardial hypertrophy

2. Coronary artery narrowing

3. Valve defect

4. Arrhythmia

Explanation: Angina occurs due to reduced blood supply from narrowed coronary arteries. Myocardial hypertrophy, valve defects, or arrhythmias may affect heart function but are not primary causes. Correct answer: 2

7. ASSERTION-REASON MCQ

Assertion (A): Angina pectoris is relieved by rest.

Reason (R): Rest reduces oxygen demand of myocardium.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. A is false but R is true

Explanation: Rest lowers myocardial oxygen demand, alleviating chest pain in angina. Therefore, both assertion and reason are true, and reason explains assertion. Correct answer: 1

8. MATCHING TYPE MCQ

Match disorder with primary symptom:

Column A:

1. Angina pectoris

2. Cardiac arrest

3. Heart failure

4. Coronary heart disease

Column B:

1. Acute chest pain

2. Sudden stoppage of heart

3. Fluid retention

4. Artery blockage

Explanation: Angina presents as acute chest pain, cardiac arrest is sudden heart stoppage, heart failure shows fluid retention, and coronary heart disease involves arterial blockage. Matching ensures correct understanding of symptoms and pathophysiology. Correct matching: 1-1, 2-2, 3-3, 4-4

9. FILL IN THE BLANKS / COMPLETION MCQ

Chest pain due to inadequate oxygen supply to heart muscles is called ________.

1. Heart failure

2. Angina pectoris

3. Cardiac arrest

4. Arrhythmia

Explanation: Angina pectoris is the medical term for chest pain caused by reduced blood and oxygen supply to the myocardium. Other options refer to different heart conditions not characterized primarily by transient chest pain. Correct answer: 2

10. CHOOSE THE CORRECT STATEMENTS MCQ

Statement I: Angina is a symptom of myocardial ischemia.
Statement II: Coronary artery dilation can relieve angina.

1. Only Statement I is correct

2. Only Statement II is correct

3. Both Statements I and II are correct

4. Both Statements I and II are incorrect

Explanation: Angina is caused by myocardial ischemia. Vasodilators like nitroglycerin relieve angina by increasing oxygen supply. Therefore, both statements are correct and consistent with the pathophysiology. Correct answer: 3

Topic: Endocrine Regulation of Blood Pressure; Subtopic: Hormonal Control of Cardiovascular System

Keyword Definitions:

• Antidiuretic Hormone (ADH): Hormone secreted by posterior pituitary that increases water reabsorption in kidneys, raising blood pressure.

• Atrial Natriuretic Factor (ANF): Peptide hormone produced by atria of heart, promoting sodium and water excretion to reduce blood volume and pressure.

• Aldosterone: Mineralocorticoid hormone from adrenal cortex that increases sodium reabsorption in kidneys, indirectly increasing blood pressure.

• Angiotensin-II: Potent vasoconstrictor hormone that increases blood pressure by narrowing blood vessels and stimulating aldosterone secretion.

• Blood Pressure: Force exerted by circulating blood on walls of blood vessels, regulated by neural and hormonal mechanisms.

• Kidney: Organ responsible for maintaining fluid and electrolyte balance, and controlling blood pressure through renin-angiotensin-aldosterone system.

• Vasodilation: Widening of blood vessels to reduce vascular resistance and lower blood pressure.

• Hormonal Regulation: Control of physiological processes by hormones secreted by endocrine glands.

Lead Question - 2022 (Abroad)
Which one of the following hormones reduces the blood pressure?
1. Antidiuretic hormone
2. Atrial Natriuretic factor
3. Aldosterone
4. Angiotensin-II
Explanation: The correct answer is Atrial Natriuretic factor. ANF is released from the atrial walls of the heart in response to high blood volume or pressure. It promotes natriuresis, the excretion of sodium and water by kidneys, leading to decreased blood volume and vasodilation, which together reduce blood pressure. Unlike ADH, aldosterone, and angiotensin-II, which increase blood pressure through water retention or vasoconstriction, ANF serves as a counter-regulatory hormone, maintaining cardiovascular homeostasis. It is essential in preventing hypertension and maintaining proper fluid and electrolyte balance, acting directly on renal tubules and blood vessels to lower vascular resistance and circulating volume.

1. Single Correct Answer Type:
Which hormone promotes water retention and increases blood pressure?
1. Atrial Natriuretic factor
2. Antidiuretic hormone
3. Prolactin
4. Cortisol
Explanation: The correct answer is Antidiuretic hormone. ADH is secreted by the posterior pituitary in response to dehydration or low blood volume. It increases water reabsorption in renal collecting ducts, reducing urine output, and raising blood pressure. ANF, in contrast, decreases blood pressure. ADH does not directly influence sodium excretion like aldosterone, and prolactin and cortisol have different physiological functions. By maintaining blood volume, ADH is crucial for cardiovascular homeostasis, especially during fluid deficit or hemorrhage.

2. Single Correct Answer Type:
Which hormone directly causes vasodilation to reduce blood pressure?
1. Angiotensin-II
2. Atrial Natriuretic factor
3. Aldosterone
4. ADH
Explanation: The correct answer is Atrial Natriuretic factor. ANF binds to receptors on vascular smooth muscles and kidney cells, inducing vasodilation and promoting excretion of sodium and water. This combination lowers vascular resistance and blood volume, thereby decreasing blood pressure. Angiotensin-II and aldosterone increase pressure, and ADH primarily increases water reabsorption. ANF plays a crucial counter-regulatory role against hypertensive stimuli, maintaining homeostasis in the cardiovascular system and protecting organs from damage due to elevated blood pressure.

3. Single Correct Answer Type:
Aldosterone reduces blood pressure by:
1. Increasing sodium excretion
2. Increasing sodium retention
3. Promoting vasodilation
4. Inhibiting renin
Explanation: The correct answer is Increasing sodium retention. Aldosterone is a mineralocorticoid secreted from the adrenal cortex. It promotes sodium reabsorption in renal distal tubules and collecting ducts, leading to water retention and increased blood volume, which raises blood pressure. It does not reduce pressure or promote vasodilation. ANF, not aldosterone, reduces blood pressure. Aldosterone’s action is part of the renin-angiotensin-aldosterone system that regulates fluid balance and blood pressure, crucial for maintaining homeostasis in response to hypotension or low blood volume.

4. Single Correct Answer Type:
Angiotensin-II increases blood pressure primarily by:
1. Stimulating vasodilation
2. Stimulating aldosterone secretion and vasoconstriction
3. Inhibiting ADH
4. Increasing sodium excretion
Explanation: The correct answer is Stimulating aldosterone secretion and vasoconstriction. Angiotensin-II is a potent vasoconstrictor that narrows arterioles, increasing vascular resistance. It also stimulates aldosterone release from adrenal cortex, promoting sodium and water retention, which raises blood volume and pressure. This mechanism contrasts with ANF, which lowers blood pressure. Angiotensin-II is central to the renin-angiotensin-aldosterone system, regulating blood pressure and fluid balance in response to hypotension or dehydration, ensuring adequate perfusion to vital organs.

5. Single Correct Answer Type:
Which hormone’s release is triggered by increased atrial stretch due to high blood volume?
1. ADH
2. ANF
3. Aldosterone
4. Angiotensin-II
Explanation: The correct answer is ANF. Atrial Natriuretic Factor is secreted by atrial myocytes when they detect increased blood volume and pressure, causing atrial stretch. ANF promotes sodium and water excretion and vasodilation, effectively reducing blood pressure. ADH, aldosterone, and angiotensin-II have opposite effects, conserving water and increasing pressure. ANF acts as a counter-regulatory hormone to prevent hypertension, maintain fluid balance, and protect cardiovascular tissues, ensuring homeostasis in response to volume overload conditions.

6. Single Correct Answer Type:
Which hormone counteracts the effects of aldosterone?
1. ADH
2. Angiotensin-II
3. Atrial Natriuretic factor
4. Cortisol
Explanation: The correct answer is Atrial Natriuretic factor. ANF opposes aldosterone by promoting sodium and water excretion and vasodilation, reducing blood pressure. Aldosterone promotes sodium and water retention to raise pressure, while ANF decreases blood volume and vascular resistance. ADH and angiotensin-II enhance water retention and increase blood pressure. ANF maintains cardiovascular homeostasis, preventing hypertension and regulating fluid balance, acting as a physiological antagonist to the renin-angiotensin-aldosterone system.

7. Assertion-Reason Type:
Assertion (A): ANF lowers blood pressure.
Reason (R): ANF promotes sodium and water excretion and vasodilation.
1. Both A and R are correct, and R is the correct explanation of A
2. Both A and R are correct, but R is not the correct explanation of A
3. A is correct, R is false
4. A is false, R is true
Explanation: Correct answer is Both A and R are correct, and R is the correct explanation of A. ANF reduces blood pressure by promoting natriuresis and diuresis, decreasing blood volume. Additionally, it induces vasodilation, lowering vascular resistance. Together, these mechanisms counteract the effects of hormones like aldosterone and angiotensin-II, maintaining cardiovascular homeostasis. This regulation is critical for preventing hypertension, ensuring proper perfusion of organs, and protecting cardiac tissues from volume overload.

8. Matching Type:
Match the hormone with its primary effect on blood pressure:
A. ADH → (i) Decreases BP
B. ANF → (ii) Increases BP
C. Aldosterone → (iii) Increases BP via sodium retention
D. Angiotensin-II → (iv) Increases BP via vasoc

Topic: Circulatory System; Subtopic: Heart and Cardiac Function

Keyword Definitions:
- Tricuspid valve: Valve between right atrium and right ventricle.
- Bicuspid valve (Mitral valve): Valve between left atrium and left ventricle.
- Semilunar valves: Pulmonary and aortic valves controlling blood flow out of ventricles.
- Diastole: Relaxation phase of the heart chambers.
- Systole: Contraction phase of the heart chambers.
- Atria: Upper chambers of the heart receiving blood.
- Ventricles: Lower chambers pumping blood to lungs and body.
- Atrioventricular node (AVN): Node generating impulses for ventricular contraction.
- Action potential: Electrical signal initiating cardiac muscle contraction.
- Cardiac cycle: Sequence of atrial and ventricular contraction and relaxation.
- Blood circulation: Movement of blood through heart, lungs, and body.

Lead Question - 2022:
Which one of the following statements is correct?
(1) The tricuspid and the bicuspid valves open due to the pressure exerted by the simultaneous contraction of the atria
(2) Blood moves freely from atrium to the ventricle during joint diastole
(3) Increased ventricular pressure causes closing of the semilunar valves
(4) The atrio-ventricular node (AVN) generates an action potential to stimulate atrial contraction

Explanation: The correct answer is (3). Increased ventricular pressure during systole causes the semilunar valves to close, preventing backflow into atria. Tricuspid and bicuspid valves open due to atrial pressure, not simultaneous contraction. AVN stimulates ventricular, not atrial, contraction. Blood moves from atrium to ventricle mainly during atrial systole.

1. Single Correct Answer:
Which valve prevents backflow into the left ventricle?
(a) Tricuspid
(b) Bicuspid
(c) Aortic semilunar
(d) Pulmonary semilunar
Explanation: The aortic semilunar valve prevents backflow from the aorta into the left ventricle. Tricuspid and bicuspid valves prevent backflow into atria, and pulmonary semilunar valve prevents backflow from pulmonary artery into right ventricle.

2. Single Correct Answer:
Which chamber receives oxygenated blood from lungs?
(a) Right atrium
(b) Left atrium
(c) Right ventricle
(d) Left ventricle
Explanation: The left atrium receives oxygenated blood from the lungs via pulmonary veins. Right atrium receives deoxygenated blood, and ventricles pump blood to lungs and body.

3. Single Correct Answer:
During which phase do ventricles contract?
(a) Atrial diastole
(b) Ventricular systole
(c) Atrial systole
(d) Ventricular diastole
Explanation: Ventricular systole is the phase when ventricles contract to pump blood into the aorta and pulmonary artery. Atrial systole fills the ventricles, and diastole refers to relaxation phases of heart chambers.

4. Single Correct Answer:
Which node initiates the heartbeat?
(a) AVN
(b) SA node
(c) Purkinje fibers
(d) Bundle of His
Explanation: The SA node generates action potentials initiating the heartbeat, causing atrial contraction. AVN transmits impulses to ventricles, Purkinje fibers distribute signals, and Bundle of His conducts impulses but does not initiate them.

5. Single Correct Answer:
Which valves open due to atrial pressure?
(a) Semilunar valves
(b) Tricuspid and bicuspid valves
(c) Aortic valve
(d) Pulmonary valve
Explanation: Tricuspid and bicuspid valves open when atrial pressure exceeds ventricular pressure, allowing blood to flow into ventricles. Semilunar valves open when ventricular pressure exceeds arterial pressure to pump blood out.

6. Single Correct Answer:
Which fibers distribute impulses to ventricular myocardium?
(a) SA node fibers
(b) AVN fibers
(c) Purkinje fibers
(d) Bundle of His
Explanation: Purkinje fibers rapidly conduct action potentials throughout ventricles, ensuring coordinated contraction. SA node initiates heartbeat, AVN delays impulse, and Bundle of His conducts impulses from AVN to ventricles.

7. Assertion-Reason MCQ:
Assertion (A): Semilunar valves prevent backflow during ventricular relaxation.
Reason (R): Semilunar valves close when ventricular pressure falls below arterial pressure.
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: Option (a) is correct. Semilunar valves close during ventricular diastole to prevent backflow. This occurs when ventricular pressure falls below arterial pressure. Both assertion and reason are true, and R directly explains A.

8. Matching Type MCQ:
Match cardiac components with their function:
List - I List - II
(a) SA node (i) Initiates heartbeat
(b) AV node (ii) Delays impulse
(c) Purkinje fibers (iii) Distributes impulse to ventricles
(d) Tricuspid valve (iv) Prevents backflow into atrium
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-iii, b-iv, c-i, d-ii
(4) a-iv, b-iii, c-ii, d-i
Explanation: Option (1) is correct. SA node initiates heartbeat, AV node delays impulses, Purkinje fibers distribute impulses to ventricles, and tricuspid valve prevents backflow into right atrium, ensuring coordinated cardiac function.

9. Fill in the Blanks:
Blood moves from atrium to ventricle mainly during _______
(a) Ventricular systole
(b) Ventricular diastole
(c) Atrial systole
(d) Atrial diastole
Explanation: Blood moves from atrium to ventricle mainly during atrial systole. Ventricular contraction pumps blood into arteries. Ventricular diastole allows filling of ventricles, and atrial diastole corresponds to relaxation of atria.

10. Choose the Correct Statements:
Identify correct statements:
1. AV node delays impulses for ventricular filling.
2. Semilunar valves open during ventricular systole.
3. SA node initiates atrial and ventricular contraction simultaneously.

Topic: Blood and Circulation
Subtopic: Coagulation and Spleen Function

Keyword Definitions:
• Coagulum: A mass formed during blood clotting consisting of fibrin and trapped blood cells.
• Thrombin: Enzyme that converts fibrinogen into fibrin during coagulation.
• Fibrin: Insoluble protein threads forming the mesh in a blood clot.
• Spleen: Organ involved in filtration of blood, removal of old erythrocytes, and immune responses.
• Erythrocytes: Red blood cells responsible for oxygen transport.
• Platelets: Small cell fragments that aid in clot formation.
• Hemostasis: Process of stopping bleeding through vascular constriction, platelet plug, and clot formation.
• Clotting Factors: Plasma proteins involved in blood coagulation.
• Fibrinolysis: Process of clot breakdown after tissue repair.
• Reticuloendothelial System: Network including spleen that removes old blood cells and debris.

Lead Question (2022):
Given below are two statements:
Statement I: The coagulum is formed of network of threads called thrombins.
Statement II: Spleen is the graveyard of erythrocytes.
In the light of the above statements, choose the most appropriate answer from the options given below:
1. Both Statement I and Statement II are incorrect
2. Statement I is correct but Statement II is incorrect
3. Statement I is incorrect but Statement II is correct
4. Both Statement I and Statement II are correct

Explanation: The correct answer is 3. Statement I is incorrect because coagulum is formed of fibrin threads, not thrombins. Statement II is correct since the spleen removes aged and damaged erythrocytes from circulation, acting as the “graveyard” of red blood cells, and also contributes to immune surveillance.

Guessed MCQs:

1. Which enzyme converts fibrinogen to fibrin during coagulation?
Options:
(a) Thrombin
(b) Plasmin
(c) Prothrombin
(d) Heparin
Explanation: The correct answer is (a) Thrombin. Thrombin catalyzes the conversion of soluble fibrinogen into insoluble fibrin, forming the structural basis of a blood clot. Plasmin breaks clots, prothrombin is the inactive precursor of thrombin, and heparin is an anticoagulant.

2. Which cells primarily initiate platelet plug formation?
Options:
(a) Platelets
(b) Erythrocytes
(c) Leukocytes
(d) Endothelial cells
Explanation: The correct answer is (a) Platelets. Platelets adhere to damaged endothelium, release granules, and aggregate to form a temporary plug. Erythrocytes, leukocytes, and endothelial cells have supporting roles in coagulation and inflammation but do not initiate platelet plug formation.

3. Assertion-Reason MCQ:
Assertion (A): Fibrinolysis prevents excessive clot formation.
Reason (R): Plasminogen is converted to plasmin, which digests fibrin.
Options:
(a) Both A and R are true, R explains A
(b) Both A and R are true, R does not explain A
(c) A is true, R is false
(d) A is false, R is true
Explanation: The correct answer is (a). Fibrinolysis dissolves clots after tissue repair to prevent thrombosis. Plasminogen activation to plasmin digests fibrin, ensuring controlled clot removal and maintaining blood flow, explaining the physiological significance of fibrinolysis.

4. Matching Type MCQ:
Match the component with its function:
List - I List - II
(a) Spleen (i) Removes old erythrocytes
(b) Platelets (ii) Initiate clot formation
(c) Thrombin (iii) Converts fibrinogen to fibrin
Options:
1. a-i, b-ii, c-iii
2. a-ii, b-i, c-iii
3. a-i, b-iii, c-ii
4. a-iii, b-ii, c-i
Explanation: The correct answer is 1. The spleen removes aged red blood cells, platelets initiate the formation of a platelet plug, and thrombin converts fibrinogen into fibrin, forming the structural network of a coagulum, essential for hemostasis.

5. Which vitamin is essential for synthesis of clotting factors?
Options:
(a) Vitamin K
(b) Vitamin D
(c) Vitamin C
(d) Vitamin B12
Explanation: The correct answer is (a) Vitamin K. Vitamin K is required for γ-carboxylation of glutamate residues in clotting factors II, VII, IX, and X, essential for coagulation. Vitamin D regulates calcium metabolism, C aids collagen synthesis, and B12 supports erythropoiesis.

6. Single Correct Answer:
Which plasma protein is converted into fibrin during coagulation?
Options:
(a) Fibrinogen
(b) Albumin
(c) Globulin
(d) Hemoglobin
Explanation: The correct answer is (a) Fibrinogen. Fibrinogen is a soluble plasma protein converted to insoluble fibrin by thrombin during clot formation. Albumin maintains osmotic pressure, globulins are antibodies, and hemoglobin carries oxygen.

7. Fill in the Blanks:
The breakdown of blood clots after healing is called __________.
Options:
(a) Fibrinolysis
(b) Hemostasis
(c) Thrombosis
(d) Coagulation
Explanation: The correct answer is (a) Fibrinolysis. Fibrinolysis involves plasmin-mediated degradation of fibrin, removing clots after tissue repair. Hemostasis stops bleeding, thrombosis is pathological clot formation, and coagulation is clot formation.

8. Which organ stores platelets and filters blood?
Options:
(a) Spleen
(b) Liver
(c) Kidney
(d) Heart
Explanation: The correct answer is (a) Spleen. The spleen stores platelets, filters aged red cells, and participates in immune responses. Liver produces clotting factors, kidney filters plasma, and heart pumps blood but does not store platelets.

9. Single Correct Answer:
Which ion is required for multiple steps of coagulation cascade?
Options:
(a) Calcium
(b) Sodium
(c) Potassium
(d) Magnesium
Explanation: The correct answer is (a) Calcium. Calcium ions (Ca2+) act as cofactors for several coagulation enzymes, facilitating thrombin formation and fibrin stabilization. Sodium, potassium, and magnesium have other physiological roles but are not primary cofactors in coagulation.

10. Choose the correct statements:
(i) Fibrin forms the structural network of a clot
(ii) Spleen removes damaged erythrocytes
(iii) Thrombin forms the coagulum threads
(iv) Platelets initiate clot formation
Options:
(a) i, ii, iv
(b) i, iii, iv
(c) ii, iii, iv
(d) i, ii, iii, iv
Explanation: The correct answer is (a) i, ii, iv. Fibrin forms clot network, spleen removes old red blood cells, and platelets initiate clot formation. Thrombin converts fibrinogen to fibrin but does not form threads directly.

Subtopic: ABO Blood Group

• AB Blood Group: Blood group with both A and B antigens on RBC surface.

• Universal Recipient: Person who can receive blood from any ABO type due to absence of anti-A and anti-B antibodies in plasma.

• Antigens: Molecules on red blood cells recognized by the immune system.

• Antibodies: Proteins in plasma that react against foreign antigens.

• RBC (Red Blood Cells): Cells carrying oxygen and antigens on their surface.

• Plasma: Liquid component of blood containing antibodies, proteins, and nutrients.

• Blood transfusion: Transfer of blood or components from donor to recipient.

• Compatibility: Matching blood types to prevent agglutination during transfusion.

• A Blood Group: RBCs have A antigen and anti-B antibodies in plasma.

• B Blood Group: RBCs have B antigen and anti-A antibodies in plasma.

• O Blood Group: RBCs lack A and B antigens but plasma has both anti-A and anti-B antibodies.

Lead Question - 2021

Persons with 'AB' blood group are called as "Universal recipients". This is due to:

(1) Absence of antigens A and B in plasma
(2) Presence of antibodies, anti-A and anti-B, on RBCs
(3) Absence of antibodies, anti-A and anti-B, in plasma
(4) Absence of antigens A and B on the surface of RBCs

Explanation: Persons with AB blood group have both A and B antigens on RBCs but lack anti-A and anti-B antibodies in plasma. This absence of antibodies allows them to receive blood from any ABO group without immune reaction. Answer: Absence of antibodies, anti-A and anti-B, in plasma.

1. Single Correct Answer MCQ: Which blood group is called universal donor?
Options:
A. AB
B. O
C. A
D. B

Explanation: O blood group lacks A and B antigens on RBCs, preventing immune reactions in recipients. Therefore, O blood is universal donor. Answer: O.

2. Single Correct Answer MCQ: Which antibodies are present in plasma of B blood group?
Options:
A. Anti-A
B. Anti-B
C. Anti-A and Anti-B
D. None

Explanation: B blood group has B antigen on RBCs and anti-A antibodies in plasma to react against A antigens. Answer: Anti-A.

3. Single Correct Answer MCQ: Blood transfusion reaction occurs when:
Options:
A. Donor RBC antigens match recipient antibodies
B. Donor RBC antigens do not match recipient antibodies
C. Both donor and recipient are AB
D. Both donor and recipient are O

Explanation: Agglutination happens if donor RBC antigens are recognized by recipient antibodies, causing transfusion reaction. Answer: Donor RBC antigens match recipient antibodies.

4. Single Correct Answer MCQ: Plasma of O blood group contains:
Options:
A. No antibodies
B. Anti-A only
C. Anti-B only
D. Anti-A and Anti-B

Explanation: O blood group RBCs lack A and B antigens, so plasma has both anti-A and anti-B antibodies to prevent reaction against any donor antigens. Answer: Anti-A and Anti-B.

5. Single Correct Answer MCQ: Which antigen is present on RBCs of AB blood group?
Options:
A. A only
B. B only
C. Both A and B
D. None

Explanation: AB blood group has both A and B antigens on the surface of RBCs, allowing compatibility with any donor. Answer: Both A and B.

6. Single Correct Answer MCQ: Blood group lacking both antigens on RBCs is:
Options:
A. AB
B. O
C. A
D. B

Explanation: O blood group lacks A and B antigens, making it compatible with all recipients. Answer: O.

7. Assertion-Reason MCQ:
Assertion (A): AB blood group persons are universal recipients.
Reason (R): AB plasma contains anti-A and anti-B antibodies.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: AB persons are universal recipients because plasma lacks anti-A and anti-B antibodies. Reason given is false. Answer: A true, R false.

8. Matching Type MCQ:
Column I: 1. Universal donor 2. Universal recipient 3. Has anti-A 4. Has anti-B
Column II: A. O blood group B. AB blood group C. B blood group D. A blood group
Options:
A. 1-A, 2-B, 3-D, 4-C
B. 1-B, 2-A, 3-C, 4-D
C. 1-A, 2-B, 3-C, 4-D
D. 1-A, 2-B, 3-D, 4-B

Explanation: O blood group is universal donor, AB is universal recipient, B group has anti-A, A group has anti-B. Answer: 1-A, 2-B, 3-D, 4-C.

9. Fill in the Blank MCQ: The plasma of AB blood group has ______ antibodies.
Options:
A. Anti-A
B. Anti-B
C. Both anti-A and anti-B
D. None

Explanation: AB plasma lacks both anti-A and anti-B antibodies, allowing safe reception from all ABO groups. Answer: None.

10. Choose the correct statements MCQ:
(a) AB blood group has both A and B antigens.
(b) AB blood group lacks anti-A and anti-B antibodies.
(c) O blood group is universal recipient.
(d) O blood group lacks antigens A and B.
Options:
1. (a), (b), (d) only
2. (a) and (b) only
3. (b) and (c) only
4. All of the above

Explanation: AB group has both antigens and no antibodies; O group lacks antigens and is universal donor, not recipient. Correct statements: (a), (b), (d). Answer: (a), (b), (d) only.

Subtopic: Coagulation and Hemostasis

• Fibrinogen: Soluble plasma protein produced by liver, converted to fibrin during blood clotting.

• Fibrin: Insoluble protein threads forming the mesh of a blood clot.

• Thrombin: Enzyme that catalyzes conversion of fibrinogen to fibrin in the coagulation cascade.

• Renin: Kidney enzyme regulating blood pressure, not involved in clotting.

• Epinephrine: Hormone involved in fight-or-flight response, not in coagulation.

• Thrombokinase: Also called tissue factor, activates clotting cascade to generate thrombin.

• Coagulation: Process of blood clot formation to prevent bleeding.

• Platelets: Blood cells that initiate clot formation by releasing clotting factors.

• Hemostasis: Sequence of events to stop bleeding: vasoconstriction, platelet plug, coagulation.

• Clotting factors: Proteins in plasma that act sequentially to form a fibrin clot.

• Prothrombin: Plasma protein converted to thrombin by clotting factors during coagulation.

Lead Question - 2021

Which enzyme is responsible for the conversion of inactive fibrinogens to fibrins?

(1) Renin
(2) Epinephrine
(3) Thrombokinase
(4) Thrombin

Explanation: Thrombin is the enzyme that converts soluble fibrinogen into insoluble fibrin during blood coagulation. Thrombokinase (tissue factor) activates prothrombin to thrombin. Renin regulates blood pressure and epinephrine is a hormone. The clot is formed by a fibrin mesh, stabilizing hemostasis. Answer: Thrombin.

1. Single Correct Answer MCQ: Which plasma protein is converted to fibrin by thrombin?
Options:
A. Albumin
B. Fibrinogen
C. Globulin
D. Prothrombin

Explanation: Fibrinogen is a soluble plasma protein that thrombin converts into insoluble fibrin, forming the structural basis of a blood clot. Prothrombin is converted to thrombin. Answer: Fibrinogen.

2. Single Correct Answer MCQ: Thrombokinase mainly functions to:
Options:
A. Convert fibrinogen to fibrin
B. Activate prothrombin to thrombin
C. Break down clots
D. Regulate blood pressure

Explanation: Thrombokinase, also called tissue factor, initiates the clotting cascade by activating prothrombin to thrombin. Thrombin then converts fibrinogen to fibrin. Answer: Activate prothrombin to thrombin.

3. Single Correct Answer MCQ: Which factor directly forms the fibrin mesh in clotting?
Options:
A. Prothrombin
B. Thrombin
C. Fibrinogen
D. Platelets

Explanation: Thrombin acts on fibrinogen to produce insoluble fibrin strands, forming the fibrin mesh that stabilizes blood clots. Platelets provide a surface for clotting but do not form fibrin. Answer: Thrombin.

4. Single Correct Answer MCQ: Which organ produces fibrinogen?
Options:
A. Kidney
B. Liver
C. Spleen
D. Bone marrow

Explanation: Liver synthesizes fibrinogen, a soluble plasma protein required for coagulation. Deficiency impairs clot formation. Other organs do not produce fibrinogen. Answer: Liver.

5. Single Correct Answer MCQ: Which enzyme is not involved in coagulation?
Options:
A. Thrombin
B. Thrombokinase
C. Renin
D. Factor X

Explanation: Renin regulates blood pressure and the renin-angiotensin system, not coagulation. Thrombin, thrombokinase, and Factor X are part of the clotting cascade. Answer: Renin.

6. Single Correct Answer MCQ: Thrombin converts fibrinogen into:
Options:
A. Prothrombin
B. Fibrin
C. Plasmin
D. Collagen

Explanation: Thrombin catalyzes the conversion of soluble fibrinogen into insoluble fibrin, which forms the mesh stabilizing blood clots. Answer: Fibrin.

7. Assertion-Reason MCQ:
Assertion (A): Thrombin is essential for blood coagulation.
Reason (R): It converts fibrinogen to fibrin forming the clot matrix.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Thrombin is essential as it converts fibrinogen into insoluble fibrin, forming the clot. This explains its key role in hemostasis. Both assertion and reason are correct, with reason explaining the assertion. Answer: Both A and R true, R correct explanation.

8. Matching Type MCQ:
Column I: 1. Fibrinogen 2. Prothrombin 3. Thrombokinase 4. Thrombin
Column II: A. Activated by tissue factor B. Converted to fibrin C. Soluble plasma protein D. Enzyme converting fibrinogen
Options:
A. 1-C, 2-A, 3-D, 4-B
B. 1-C, 2-A, 3-A, 4-D
C. 1-B, 2-C, 3-A, 4-D
D. 1-C, 2-D, 3-A, 4-B

Explanation: Fibrinogen is soluble plasma protein, prothrombin is activated by thrombokinase, thrombin converts fibrinogen to fibrin. Correct matching: 1-C, 2-A, 3-A, 4-D. Answer: 1-C, 2-A, 3-A, 4-D.

9. Fill in the Blank MCQ: _______ converts fibrinogen into insoluble fibrin during coagulation.
Options:
A. Renin
B. Thrombin
C. Epinephrine
D. Thrombokinase

Explanation: Thrombin is the enzyme responsible for converting soluble fibrinogen into insoluble fibrin threads that form the structural clot. Answer: Thrombin.

10. Choose the correct statements MCQ:
(a) Thrombin converts fibrinogen to fibrin.
(b) Thrombokinase activates prothrombin.
(c) Renin converts fibrinogen to fibrin.
(d) Fibrin forms the clot matrix.
Options:
1. (a), (b), (d) only
2. (a), (c), (d) only
3. (b) and (c) only
4. All of the above

Explanation: Thrombin converts fibrinogen to fibrin, thrombokinase activates prothrom

Subtopic: Hormonal Regulation of Blood Cells

• Erythropoietin (EPO): Hormone that stimulates red blood cell production in the bone marrow.

• Juxtaglomerular Cells: Specialized kidney cells that detect blood oxygen levels and secrete erythropoietin.

• Rostral Adenohypophysis: Anterior pituitary lobe that secretes various hormones, not EPO.

• Alpha Cells: Pancreatic cells that secrete glucagon, not EPO.

• Bone Marrow: Site of hematopoiesis where erythrocytes are produced.

• RBC Formation: Production of red blood cells stimulated by erythropoietin.

• Hypoxia: Low oxygen levels in tissues triggering erythropoietin release.

• Endocrine Hormones: Chemical messengers secreted by glands into blood to regulate body functions.

• Feedback Regulation: Mechanism controlling hormone release based on physiological need.

• Hematopoietic Stem Cells: Precursor cells in bone marrow giving rise to blood cells.

• Kidney Function: Erythropoietin secretion is part of kidney response to hypoxia.

Lead Question - 2021

Erythropoietin hormone which stimulates R.B.C. formation is produced by :

Options:
1. The cells of rostral adenohypophysis
2. The cells of bone marrow
3. Juxtaglomerular cells of the kidney
4. Alpha cells of pancreas

Explanation: Erythropoietin is secreted by juxtaglomerular cells of the kidney in response to hypoxia. It stimulates the bone marrow to produce red blood cells, ensuring oxygen transport in the body. Pituitary and pancreatic cells do not secrete this hormone. Answer: Juxtaglomerular cells of the kidney.

1. Which condition triggers erythropoietin secretion?
Options:
A. High oxygen levels
B. Low oxygen levels (hypoxia)
C. High glucose
D. Low calcium

Explanation: Hypoxia or low oxygen concentration stimulates juxtaglomerular cells to secrete erythropoietin, enhancing RBC production to improve oxygen delivery. High oxygen or unrelated signals like glucose do not trigger EPO. Answer: Low oxygen levels (hypoxia).

2. What is the main site of RBC production stimulated by erythropoietin?
Options:
A. Kidney
B. Liver
C. Bone marrow
D. Spleen

Explanation: Bone marrow contains hematopoietic stem cells that differentiate into erythrocytes. Erythropoietin secreted by kidney cells acts on these stem cells to increase RBC production. The kidney produces the hormone, not the cells directly. Answer: Bone marrow.

3. Which organ does not produce erythropoietin?
Options:
A. Kidney
B. Liver (adult)
C. Rostral adenohypophysis
D. Juxtaglomerular cells

Explanation: In adults, the kidney juxtaglomerular cells secrete erythropoietin. The rostral adenohypophysis (anterior pituitary) does not produce EPO. The fetal liver can produce some EPO, but in adults, liver contribution is minimal. Answer: Rostral adenohypophysis.

4. Erythropoietin primarily acts on:
Options:
A. Alpha cells of pancreas
B. Hematopoietic stem cells in bone marrow
C. Kidney tubules
D. Liver hepatocytes

Explanation: Erythropoietin targets hematopoietic stem cells in the bone marrow to stimulate proliferation and differentiation into red blood cells, thereby increasing oxygen-carrying capacity. Other organs are not the primary targets. Answer: Hematopoietic stem cells in bone marrow.

5. Which pancreatic cells are unrelated to erythropoietin?
Options:
A. Beta cells
B. Alpha cells
C. Delta cells
D. All of the above

Explanation: Pancreatic cells, including alpha, beta, and delta cells, secrete hormones like glucagon, insulin, and somatostatin. They are unrelated to erythropoietin secretion. Kidney juxtaglomerular cells produce EPO, not pancreatic cells. Answer: All of the above.

6. Which of these hormones regulates RBC production?
Options:
A. Insulin
B. Erythropoietin
C. Cortisol
D. Thyroxine

Explanation: Erythropoietin specifically regulates red blood cell formation by acting on bone marrow hematopoietic stem cells. Other hormones regulate metabolism, stress, or growth. Answer: Erythropoietin.

7. Assertion-Reason:
Assertion (A): Kidney secretes erythropoietin in response to hypoxia.
Reason (R): Low oxygen stimulates juxtaglomerular cells to produce EPO.
Options:
A. Both A and R are true, R is correct explanation
B. Both A and R are true, R is not correct explanation
C. A is true, R is false
D. A is false, R is true

Explanation: The kidney detects hypoxia and juxtaglomerular cells respond by secreting erythropoietin to stimulate RBC formation in bone marrow. The reason accurately explains the assertion. Answer: Both A and R are true, R is correct explanation.

8. Match the following:
Column I: 1. Erythropoietin 2. Alpha cells 3. Beta cells 4. Delta cells
Column II: A. Secretes insulin B. Secretes glucagon C. Stimulates RBC production D. Secretes somatostatin
Options:
A. 1-C, 2-B, 3-A, 4-D
B. 1-B, 2-C, 3-D, 4-A
C. 1-A, 2-B, 3-C, 4-D
D. 1-D, 2-A, 3-B, 4-C

Explanation: Correct matching: Erythropoietin – RBC production (C), Alpha cells – Glucagon (B), Beta cells – Insulin (A), Delta cells – Somatostatin (D). Answer: 1-C, 2-B, 3-A, 4-D.

Subtopic: Regulation of Heart Rate and Cardiac Output

Keyword Definitions:
Cardiac Output: The volume of blood pumped by the heart per minute, product of heart rate and stroke volume.
Sympathetic nerves: Part of autonomic nervous system, increases heart rate and cardiac output.
Parasympathetic neural signals: Autonomic nerves that decrease heart rate and cardiac output.
Pneumotaxic center: Brainstem region controlling breathing pattern, not directly cardiac output.
Adrenal medullary hormones: Epinephrine and norepinephrine released from adrenal medulla, increase heart rate and cardiac output.
Stroke Volume: Amount of blood ejected by the ventricle per beat.
Autonomic Nervous System: Regulates involuntary body functions including heart rate and blood pressure.
Heart Rate: Number of heartbeats per minute.

Lead Question - 2020 (COVID Reexam):
Which of the following is associated with a decrease in cardiac output?
1. Sympathetic nerves
2. Parasympathetic neural signals
3. Pneumotaxic center
4. Adrenal medullary hormones
Explanation: Parasympathetic neural signals reduce heart rate and stroke volume, resulting in decreased cardiac output. Sympathetic nerves and adrenal medullary hormones increase heart rate and cardiac output. The pneumotaxic center regulates breathing and has no direct effect on cardiac output. Correct answer is 2. Parasympathetic neural signals.

1. Single Correct Answer MCQ:
Which nervous system increases cardiac output?
1. Parasympathetic
2. Sympathetic
3. Enteric
4. Somatic
Explanation: Sympathetic nerves increase heart rate and stroke volume, elevating cardiac output. Parasympathetic decreases it, enteric regulates gut, and somatic controls voluntary muscles. Correct answer is 2. Sympathetic.

2. Single Correct Answer MCQ:
Which hormone increases heart rate and cardiac output?
1. Epinephrine
2. Acetylcholine
3. GABA
4. Dopamine
Explanation: Epinephrine, secreted by adrenal medulla, stimulates the heart to increase rate and cardiac output. Acetylcholine reduces heart rate via parasympathetic nerves. GABA and dopamine are primarily neurotransmitters with no direct cardiac output effect. Correct answer is 1. Epinephrine.

3. Single Correct Answer MCQ:
Which part of the nervous system decreases heart rate?
1. Sympathetic
2. Parasympathetic
3. Somatic
4. Enteric
Explanation: Parasympathetic nervous system slows the heart by releasing acetylcholine, decreasing cardiac output. Sympathetic increases heart rate, somatic controls voluntary muscles, and enteric regulates gut. Correct answer is 2. Parasympathetic.

4. Single Correct Answer MCQ:
Stroke volume is reduced by:
1. Sympathetic stimulation
2. Parasympathetic stimulation
3. Adrenaline
4. Thyroid hormones
Explanation: Parasympathetic stimulation reduces stroke volume by decreasing ventricular contraction strength, lowering cardiac output. Sympathetic nerves, adrenaline, and thyroid hormones enhance contraction and increase output. Correct answer is 2. Parasympathetic stimulation.

5. Single Correct Answer MCQ:
Which factor has no direct effect on cardiac output?
1. Sympathetic nerves
2. Pneumotaxic center
3. Adrenal medulla hormones
4. Parasympathetic nerves
Explanation: Pneumotaxic center regulates breathing patterns, not heart rate or stroke volume, so it does not directly affect cardiac output. Sympathetic, parasympathetic, and adrenal hormones directly influence cardiac output. Correct answer is 2. Pneumotaxic center.

6. Single Correct Answer MCQ:
Which neurotransmitter decreases cardiac output?
1. Acetylcholine
2. Norepinephrine
3. Epinephrine
4. Dopamine
Explanation: Acetylcholine is released by parasympathetic nerves and decreases heart rate, lowering cardiac output. Norepinephrine and epinephrine increase heart rate, and dopamine has limited cardiac effect. Correct answer is 1. Acetylcholine.

7. Assertion-Reason MCQ:
Assertion (A): Parasympathetic stimulation decreases cardiac output.
Reason (R): It slows heart rate and reduces stroke volume.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation of A
3. A is true, R is false
4. A is false, R is true
Explanation: Parasympathetic stimulation reduces heart rate and stroke volume, resulting in decreased cardiac output. Both statements are true, and the reason correctly explains the assertion. Correct answer is 1. Both A and R are true, R is correct explanation.

8. Matching Type MCQ:
Match the factor with its effect on cardiac output:
A. Sympathetic nerves B. Parasympathetic nerves C. Adrenal medulla hormones D. Pneumotaxic center
1. Increase CO
2. Decrease CO
3. Increase CO
4. No direct effect
Options:
1. A-1, B-2, C-3, D-4
2. A-2, B-1, C-3, D-4
3. A-1, B-3, C-2, D-4
4. A-2, B-3, C-1, D-4
Explanation: Sympathetic nerves increase cardiac output (A-1), parasympathetic nerves decrease it (B-2), adrenal medulla hormones increase it (C-3), and pneumotaxic center has no direct effect (D-4). Correct answer is 1. A-1, B-2, C-3, D-4.

9. Fill in the Blanks MCQ:
________ stimulation slows heart rate and reduces cardiac output.
1. Sympathetic
2. Parasympathetic
3. Adrenaline
4. Thyroid
Explanation: Parasympathetic stimulation releases acetylcholine, slowing the heart and reducing stroke volume, thereby lowering cardiac output. Sympathetic and adrenal hormones increase heart rate. Thyroid affects metabolism. Correct answer is 2. Parasympathetic.

10. Choose the correct statements MCQ:
Select correct statements about cardiac output regulation:
1. Sympathetic stimulation increases cardiac output
2. Parasympathetic stimulation decreases cardiac output
3. Pneumotaxic center directly increases cardiac output
4. Adrenal medulla hormones increase cardiac output
Options:
1. 1, 2, 4
2. 1 and 3
3. 2 and 3
4. 3 and 4
Explanation: Sympathetic nerves and adrenal medulla hormones increase cardiac output (1 and 4). Parasympathetic stimulation decreases it (2). Pneumotaxic center regulates breathing and does not directly affect cardiac output. Correct statements are 1, 2, 4. Correct answer is 1. 1, 2, 4.

Topic: Cardiovascular System

Subtopic: Electrocardiography (ECG)

Keyword Definitions:

• ECG (Electrocardiogram) – A recording of the electrical activity of the heart over time.

• QRS complex – Represents depolarisation of ventricles leading to ventricular contraction.

• P wave – Depolarisation of atria (auricles) before contraction.

• T wave – Repolarisation of ventricles after contraction.

• Depolarisation – Process where cardiac muscle cells lose polarity, causing contraction.

• Repolarisation – Restoration of resting membrane potential after contraction.

Lead Question - 2020

The QRS complex in a standard ECG represents:

(1) Depolarisation of ventricles
(2) Repolarisation of ventricles
(3) Repolarisation of auricles
(4) Depolarisation of auricles

Explanation: The QRS complex represents rapid depolarisation of the ventricles, leading to ventricular contraction. The atrial depolarisation is masked by the large ventricular signal. Repolarisation of ventricles occurs later, forming the T wave. Correct answer is (1) Depolarisation of ventricles.

1. Which ECG wave represents atrial depolarisation?
(1) P wave
(2) QRS complex
(3) T wave
(4) U wave

Explanation: The P wave reflects depolarisation of atria (auricles) preceding their contraction. It is the first small upward deflection in a standard ECG. Correct answer is (1) P wave.

2. Repolarisation of ventricles is indicated by which ECG wave?
(1) P wave
(2) QRS complex
(3) T wave
(4) U wave

Explanation: The T wave represents ventricular repolarisation, returning the cells to resting potential after contraction. It follows the QRS complex. Correct answer is (3) T wave.

3. What does the PR interval represent?
(1) Time between atrial and ventricular depolarisation
(2) Ventricular repolarisation
(3) Atrial contraction duration
(4) Total heart cycle time

Explanation: The PR interval measures conduction time from atrial depolarisation onset to ventricular depolarisation onset, including AV nodal delay. It reflects coordinated timing of atrial and ventricular contraction. Correct answer is (1).

4. Assertion (A): QRS complex is larger than P wave.
Reason (R): Ventricles have more muscle mass than atria.
(1) Both A and R true and R explains A
(2) Both A and R true but R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: The QRS complex is larger due to greater ventricular muscle mass, generating higher electrical potential. Both Assertion and Reason are true, and R correctly explains A. Correct answer is (1).

5. Which wave is usually absent or small in ECG recordings?
(1) P wave
(2) Q wave
(3) U wave
(4) T wave

Explanation: U wave is often absent or very small, representing repolarisation of Purkinje fibers. It is not consistently visible. Correct answer is (3) U wave.

6. Which part of ECG corresponds to ventricular contraction?
(1) P wave
(2) QRS complex
(3) T wave
(4) PR interval

Explanation: Ventricular contraction (systole) occurs immediately after the QRS complex, following depolarisation of ventricles. Correct answer is (2) QRS complex.

7. Match ECG components with their events:
a. P wave – i. Ventricular depolarisation
b. QRS complex – ii. Ventricular repolarisation
c. T wave – iii. Atrial depolarisation
(1) a-iii, b-i, c-ii
(2) a-i, b-iii, c-ii
(3) a-ii, b-i, c-iii
(4) a-iii, b-ii, c-i

Explanation: Correct matching: P wave – atrial depolarisation (a-iii), QRS complex – ventricular depolarisation (b-i), T wave – ventricular repolarisation (c-ii). Correct answer is (1).

8. Fill in the blank: The ECG wave representing repolarisation of atria is ______.
(1) P wave
(2) QRS complex
(3) T wave
(4) Usually masked by QRS

Explanation: Atrial repolarisation occurs during ventricular depolarisation and is obscured by the QRS complex in ECG. Correct answer is (4) Usually masked by QRS.

9. Single Correct Answer: The segment between end of QRS and start of T wave is called:
(1) PR segment
(2) ST segment
(3) QT interval
(4) TP segment

Explanation: The ST segment represents the time between ventricular depolarisation and repolarisation. It is important clinically to detect ischemia or infarction. Correct answer is (2) ST segment.

10. Choose the correct statements:
(a) QRS represents ventricular depolarisation
(b) P wave represents atrial depolarisation
(c) T wave represents ventricular repolarisation
(d) U wave is atrial depolarisation
(1) a, b, c only
(2) a, b only
(3) b, c, d only
(4) a, c, d only

Explanation: Correct statements: QRS – ventricular depolarisation (a), P wave – atrial depolarisation (b), T wave – ventricular repolarisation (c). U wave is not atrial depolarisation. Correct answer is (1) a, b, c only.

Subtopic: ABO Blood Group System

• ABO blood group: Classification of human blood based on presence of antigens A and B on red blood cells.

• Gene I: Gene that controls ABO blood group, located on chromosome 9 in humans.

• Alleles: Different forms of a gene; IA, IB, and i are alleles of gene I.

• IA allele: Produces antigen A on red blood cells.

• IB allele: Produces antigen B on red blood cells.

• i allele: Does not produce any antigen, resulting in blood group O.

• Codominance: Both IA and IB alleles express equally when present together.

• Phenotype: Observable characteristic or blood group type (A, B, AB, O).

• Genotype: Genetic composition of alleles (IAIA, IAi, IBIB, IBi, IAIB, ii).

• AB blood group: Result of codominant expression of IA and IB alleles.

• Blood transfusion: Medical process requiring compatible blood groups based on antigens.

Lead Question (2020): Identify the wrong statement with reference to the gene ‘I’ that controls ABO blood groups:
Options:
1. When IA and IB are present together, they express same type of sugar
2. Allele ‘i’ does not produce any sugar
3. The gene (I) has three alleles
4. A person will have only two of the three alleles

Explanation: Correct answer is 1. IA and IB alleles are codominant and express different antigens, not the same. IA produces antigen A, IB produces antigen B. The gene I has three alleles, i does not produce antigen, and an individual inherits only two alleles, one from each parent.

1. Single Correct Answer MCQ:
Which allele of gene I produces no antigen on red blood cells?
Options:
a. IA
b. IB
c. i
d. IAIB

Explanation: Correct answer is c. The i allele does not produce any antigen, resulting in blood group O. IA and IB produce A and B antigens respectively, while IAIB is a genotype representing AB blood group with both antigens expressed.

2. Single Correct Answer MCQ:
AB blood group is an example of:
Options:
a. Complete dominance
b. Codominance
c. Recessive trait
d. Incomplete dominance

Explanation: Correct answer is b. AB blood group results from codominance of IA and IB alleles, both expressed equally, producing A and B antigens on red blood cells.

3. Single Correct Answer MCQ:
A person with genotype IAi will have which blood group?
Options:
a. A
b. B
c. AB
d. O

Explanation: Correct answer is a. IAi genotype produces blood group A. IA is dominant over i, expressing antigen A on red blood cells, while i does not contribute any antigen.

4. Single Correct Answer MCQ:
How many alleles does the gene I have in humans?
Options:
a. Two
b. Three
c. Four
d. One

Explanation: Correct answer is b. The gene I controlling ABO blood groups has three alleles: IA, IB, and i, which combine in pairs to determine an individual's blood group.

5. Single Correct Answer MCQ:
Which blood group results from genotype IBIB?
Options:
a. A
b. B
c. AB
d. O

Explanation: Correct answer is b. IBIB genotype produces blood group B because IB allele produces B antigen on red blood cells, expressed homozygously in this case.

6. Single Correct Answer MCQ:
Blood group O has which genotype?
Options:
a. IAIA
b. IBi
c. ii
d. IAIB

Explanation: Correct answer is c. Blood group O occurs when both alleles are i, producing no A or B antigens on red blood cells.

7. Assertion-Reason MCQ:
Assertion (A): Blood group AB shows codominance.
Reason (R): Both IA and IB alleles express their respective antigens simultaneously.
Options:
a. Both A and R true, R explains A
b. Both A and R true, R does not explain A
c. A true, R false
d. A false, R true

Explanation: Correct answer is a. AB blood group results from codominant expression of IA and IB alleles. Both alleles express their antigens on red cells, making both assertion and reason true, and the reason correctly explains the assertion.

8. Matching Type MCQ:
Match genotype with blood group:
(a) IAIA - (i) B
(b) IAi - (ii) AB
(c) IBIB - (iii) A
(d) IAIB - (iv) O
Options:
1. a-iii, b-iii, c-i, d-ii
2. a-ii, b-i, c-iii, d-iv
3. a-iii, b-iv, c-i, d-ii
4. a-iv, b-ii, c-iii, d-i

Explanation: Correct answer is 1. IAIA and IAi produce A blood group, IBIB produces B, and IAIB produces AB, reflecting the codominance and inheritance pattern of gene I alleles.

9. Fill in the Blanks MCQ:
The allele that does not produce any antigen in ABO blood group system is ______.
Options:
a. IA
b. IB
c. i
d. IAIB

Explanation: Correct answer is c. The i allele does not produce antigen, resulting in blood group O. It is recessive and manifests only when paired as ii genotype.

10. Choose the correct statements MCQ:
Select all correct statements:
i. IA and IB are codominant
ii. i allele is recessive and produces no antigen
iii. Gene I has three alle

Topic: Blood and Immunity
Subtopic: Types and Functions of White Blood Cells

• Eosinophils: A type of white blood cell involved in combating multicellular parasites and certain infections, releasing destructive enzymes.

• Basophils: White blood cells that release histamine and other mediators during allergic reactions.

• Neutrophils: The most abundant white blood cells, responsible for phagocytosis of pathogens.

• Lymphocytes: White blood cells responsible for immune responses, including B-cells and T-cells.

• Phagocytosis: Process by which cells engulf and digest pathogens or debris.

• Histamine: Chemical released by basophils and mast cells during inflammation and allergic reactions.

• Granules: Small vesicles in cells containing enzymes or chemicals for defense or signaling.

• Immune Response: Body’s defense mechanism involving recognition and elimination of pathogens.

• White Blood Cells: Cells of the immune system involved in defending the body against infectious disease and foreign invaders.

• Destructive Enzymes: Enzymes released by eosinophils and neutrophils to destroy pathogens.

• Allergic Reaction: Immune system response to harmless substances leading to histamine release.

Lead Question (2020): Match the following columns and select the correct option:
Column - I Column - II
(a) Eosinophils (i) Immune response
(b) Basophils (ii) Phagocytosis
(c) Neutrophils (iii) Release histaminase, destructive enzymes
(d) Lymphocytes (iv) Release granules containing histamine
Options:
1. a-i, b-ii, c-iv, d-iii
2. a-ii, b-i, c-iii, d-iv
3. a-iii, b-iv, c-ii, d-i
4. a-iv, b-i, c-ii, d-iii

Explanation: Correct answer is 3. Eosinophils release histaminase and destructive enzymes, Basophils release histamine granules, Neutrophils perform phagocytosis, and Lymphocytes mediate immune responses. This arrangement reflects the specialized functions of different white blood cells in immunity.

1. Single Correct Answer MCQ:
Which white blood cell is primarily responsible for phagocytosis?
Options:
a. Eosinophils
b. Basophils
c. Neutrophils
d. Lymphocytes

Explanation: Correct answer is c. Neutrophils are the first responders to infection and engulf pathogens via phagocytosis, helping control bacterial and fungal infections efficiently.

2. Single Correct Answer MCQ:
Which white blood cells release histamine during allergic reactions?
Options:
a. Neutrophils
b. Basophils
c. Lymphocytes
d. Eosinophils

Explanation: Correct answer is b. Basophils contain granules filled with histamine, which is released during allergic responses and inflammation, contributing to vasodilation and immune signaling.

3. Single Correct Answer MCQ:
Which WBC is involved in mediating immune response?
Options:
a. Lymphocytes
b. Neutrophils
c. Eosinophils
d. Basophils

Explanation: Correct answer is a. Lymphocytes, including B-cells and T-cells, are central to adaptive immunity, producing antibodies and coordinating cellular responses against pathogens.

4. Single Correct Answer MCQ:
Which WBC combats multicellular parasites by releasing destructive enzymes?
Options:
a. Basophils
b. Neutrophils
c. Eosinophils
d. Lymphocytes

Explanation: Correct answer is c. Eosinophils release histaminase and toxic enzymes to attack multicellular parasites, such as helminths, and modulate allergic inflammation.

5. Single Correct Answer MCQ:
Which WBC contains granules with histaminase?
Options:
a. Basophils
b. Eosinophils
c. Neutrophils
d. Lymphocytes

Explanation: Correct answer is b. Eosinophils contain granules with histaminase, which inactivates histamine released during allergic responses, controlling excessive inflammation.

6. Single Correct Answer MCQ:
Which WBC is least involved in phagocytosis?
Options:
a. Neutrophils
b. Eosinophils
c. Lymphocytes
d. Basophils

Explanation: Correct answer is c. Lymphocytes mainly mediate adaptive immunity rather than phagocytosis; neutrophils and eosinophils are actively phagocytic.

7. Assertion-Reason MCQ:
Assertion (A): Basophils release histamine during allergic reactions.
Reason (R): Histamine causes vasodilation and inflammation to aid immune response.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Basophils release histamine granules; histamine increases blood flow and vessel permeability, enhancing immune cell access, making both assertion and reason true and explanatory.

8. Matching Type MCQ:
Match WBC with function:
(a) Neutrophils - (i) Immune response
(b) Lymphocytes - (ii) Phagocytosis
(c) Basophils - (iii) Release histamine
(d) Eosinophils - (iv) Release histaminase and enzymes
Options:
1. a-ii, b-i, c-iii, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-iv, b-i, c-ii, d-iii
4. a-iii, b-iv, c-i, d-ii

Explanation: Correct answer is 1. Neutrophils phagocytose, lymphocytes mediate immune response, basophils release histamine, and eosinophils release histaminase and destructive enzymes.

9. Fill in the Blanks MCQ:
________ are WBCs responsible for adaptive immunity.
Options:
a. Neutrophils
b. Basoph

Subtopic: Electrocardiography (ECG)

• P-wave: The ECG wave representing depolarisation of atria before contraction.

• QRS complex: Represents depolarisation of ventricles, leading to ventricular contraction.

• T-wave: Indicates repolarisation of ventricles after contraction.

• Repolarisation: Process of restoring the resting electrical state of the cardiac cells.

• Depolarisation: Loss of resting membrane potential, initiating muscle contraction.

• ECG: Electrocardiogram recording the electrical activity of the heart over time.

• Coronary ischemia: Reduced blood flow to heart muscles, potentially altering ECG patterns.

• Atrial activity: Electrical events occurring in atria, represented by P-wave and small repolarisation wave.

• Ventricular activity: Electrical events in ventricles, represented by QRS complex and T-wave.

• T-wave reduction: Can indicate myocardial ischemia or electrolyte imbalance.

• Heart rate: Number of heartbeats per minute, deduced from ECG intervals.

Lead Question (2019): Match the Column - I with Column -II:
Column-I | Column-II
(a) P-wave | (i) Depolarisation of ventricles
(b) QRS complex | (ii) Repolarisation of ventricles
(c) T-wave | (iii) Coronary ischemia
(d) Reduction in the size of T-wave | (iv) Depolarisation of atria
(v) Repolarisation of atria

Options:
1. a - iv, b - i, c - ii, d - iii
2. a - iv, b - i, c - ii, d - v
3. a - ii, b - i, c - v, d - iii
4. a - ii, b - iii, c - v, d - iv

Explanation: Correct answer is 1. P-wave represents depolarisation of atria, QRS complex indicates depolarisation of ventricles, T-wave shows repolarisation of ventricles, and reduction in T-wave size may indicate coronary ischemia. This mapping explains normal ECG interpretation and pathological changes in cardiac conditions.

1. Single Correct Answer MCQ:
Which ECG wave represents atrial depolarisation?
Options:
a. P-wave
b. QRS complex
c. T-wave
d. U-wave

Explanation: Correct answer is a. P-wave indicates atrial depolarisation before atrial contraction. QRS complex represents ventricular depolarisation, T-wave shows ventricular repolarisation, and U-wave may represent late repolarisation events in some individuals.

2. Single Correct Answer MCQ:
QRS complex of ECG primarily shows:
Options:
a. Atrial repolarisation
b. Ventricular depolarisation
c. Ventricular repolarisation
d. Coronary ischemia

Explanation: Correct answer is b. The QRS complex corresponds to ventricular depolarisation, triggering ventricular contraction. Atrial repolarisation is usually masked by the QRS, ventricular repolarisation is seen as T-wave, and coronary ischemia alters the QRS or T-wave patterns.

3. Single Correct Answer MCQ:
T-wave in ECG represents:
Options:
a. Ventricular depolarisation
b. Ventricular repolarisation
c. Atrial depolarisation
d. Coronary ischemia

Explanation: Correct answer is b. T-wave represents ventricular repolarisation. Ventricular depolarisation is the QRS complex, atrial depolarisation is P-wave, and coronary ischemia may cause T-wave abnormalities, including inversion or reduction in amplitude.

4. Single Correct Answer MCQ:
Reduction in T-wave amplitude may indicate:
Options:
a. Myocardial ischemia
b. Normal heart function
c. Atrial contraction
d. Ventricular depolarisation

Explanation: Correct answer is a. Decreased T-wave size can indicate coronary or myocardial ischemia, electrolyte imbalance, or other cardiac abnormalities. Normal heart function produces standard T-wave, atrial contraction generates P-wave, and ventricular depolarisation is represented by QRS complex.

5. Single Correct Answer MCQ:
Which ECG change can suggest coronary ischemia?
Options:
a. Elevated P-wave
b. Reduced T-wave
c. Normal QRS
d. Normal T-wave

Explanation: Correct answer is b. Reduction in T-wave amplitude or inversion is a key sign of myocardial ischemia. Elevated P-wave may indicate atrial enlargement, while normal QRS or T-wave suggests normal cardiac electrical activity.

6. Single Correct Answer MCQ:
Repolarisation of ventricles is represented by:
Options:
a. P-wave
b. QRS complex
c. T-wave
d. U-wave

Explanation: Correct answer is c. T-wave represents ventricular repolarisation, restoring resting membrane potential after contraction. P-wave is atrial depolarisation, QRS is ventricular depolarisation, and U-wave is occasionally seen after T-wave representing late repolarisation.

7. Assertion-Reason MCQ:
Assertion (A): P-wave represents atrial depolarisation.
Reason (R): QRS complex masks atrial repolarisation.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. P-wave shows atrial depolarisation before atrial contraction. Atrial repolarisation occurs but is obscured by QRS complex due to larger ventricular depolarisation. Both assertion and reason are correct, and reason directly explains why atrial repolarisation is not visible.

8. Matching Type MCQ:
Match ECG component with its electrical event:
(a) P-wave (i) Ventricular depolarisation
(b) QRS complex (ii) Ventricular repolarisation
(c) T-wave (iii) Atrial depolarisation
(d) Reduction in T-wave (iv) Coronary ischemia
Options:
1. a-iii, b-i, c-ii, d-iv
2. a-ii, b-i, c-iii, d-iv
3. a-iii, b-ii, c-i, d-iv
4. a-iv, b-i, c-ii, d-iii

Explanation: Correct answer is 1. P-wave corresponds to atrial depolarisation, QRS complex to ventricular depolarisation, T-wave to ventricular repolarisation, and reduction in T-wave amplitude is indicative of coronary ischemia.

9. Fill in the Blanks MCQ:
The ________ indicates ventricular depolarisation in ECG.
Options:
a. P-wave
b. QRS complex
c. T-wave
d. U-wave

Explanation: Correct answer is b. QRS complex shows depolarisation of ventricles, initiating ventricular contraction. P-wave is atrial depolarisation, T-wave is ventricular repolarisation, and U-wave represents late repolarisation in some ECGs.

10. Choose the correct statements MCQ:
Select correct statements about ECG:
i. P-wave represents atrial depolarisation
ii. QRS complex shows ventricular depolarisation
iii. T-wave represents ventricular repolarisation
iv. Reduction in T-wave may indicate coronary ischemia
Options:
a. i, ii, iii
b. i, ii, iv
c. i, iii, iv
d. i, ii, iii, iv

Explanation: Correct answer is d. All four statements are accurate: P-wave is atrial depolarisation, QRS complex is ventricular depolarisation, T-wave is ventricular repolarisation, and reduction in T-wave amplitude can suggest coronary ischemia or myocardial pathology.

Subtopic: Cardiac Output and Heart Rate

• Cardiac Output (CO): Volume of blood pumped by the heart per minute.

• Stroke Volume (SV): Volume of blood ejected by ventricles per beat.

• Heart Rate (HR): Number of heartbeats per minute.

• End-Diastolic Volume (EDV): Blood volume in ventricles at end of diastole.

• End-Systolic Volume (ESV): Blood volume remaining in ventricles after contraction.

• Ventricle: Lower chamber of heart pumping blood to body or lungs.

• Systole: Phase of heart contraction ejecting blood.

• Diastole: Phase of heart relaxation filling with blood.

• Blood Volume: Total volume of circulating blood in body.

• Pulse: Palpable beat caused by heart contraction.

• Circulatory Efficiency: Effectiveness of heart in maintaining adequate blood flow.

Lead Question (2019): What would be the heart rate of a person if the cardiac output is 5 L, blood volume in the ventricles at the end of diastole is 100 mL and at the end of ventricular systole is 50 mL :

Options:
1. 50 beats per minute
2. 75 beats per minute
3. 100 beats per minute
4. 125 beats per minute

Explanation: Correct answer is 100 beats per minute. Stroke volume (SV) = EDV – ESV = 100 – 50 = 50 mL. Cardiac output (CO) = SV × HR, thus HR = CO/SV = 5000/50 = 100 beats/min. This calculation shows the interdependence of heart rate, stroke volume, and cardiac output in circulatory physiology.

1. Single Correct Answer MCQ:
Which factor directly increases stroke volume?
Options:
a. Increased venous return
b. Decreased preload
c. Decreased contractility
d. Increased heart rate

Explanation: Correct answer is a. Increased venous return stretches ventricles more, enhancing contraction strength due to Frank-Starling mechanism. Preload is the initial stretch, contractility is intrinsic contraction strength, and heart rate does not directly affect stroke volume. Efficient stroke volume ensures optimal cardiac output and tissue perfusion.

2. Single Correct Answer MCQ:
Which phase of cardiac cycle represents ventricular filling?
Options:
a. Systole
b. Diastole
c. Isovolumetric contraction
d. Ejection

Explanation: Correct answer is b. Diastole is the phase when ventricles relax and fill with blood from atria. Systole is contraction, isovolumetric contraction occurs before ejection, and ejection is during systole. Proper diastolic filling is crucial for maintaining adequate stroke volume and cardiac output to meet tissue demands.

3. Single Correct Answer MCQ:
Which factor decreases cardiac output?
Options:
a. Increased stroke volume
b. Increased heart rate
c. Decreased venous return
d. Increased preload

Explanation: Correct answer is c. Decreased venous return reduces ventricular filling and stroke volume, lowering cardiac output. Increased stroke volume, heart rate, or preload enhances CO. Cardiac output depends on stroke volume and heart rate, and any factor limiting venous return or contraction efficiency can significantly reduce circulatory effectiveness.

4. Single Correct Answer MCQ:
Normal cardiac output at rest is approximately:
Options:
a. 2 L/min
b. 5 L/min
c. 8 L/min
d. 12 L/min

Explanation: Correct answer is b. Normal resting cardiac output is about 5 L/min, maintaining sufficient tissue perfusion. Low CO indicates heart failure or hypovolemia, while higher CO occurs during exercise. Cardiac output is a product of heart rate and stroke volume, reflecting cardiovascular efficiency and health status.

5. Single Correct Answer MCQ:
Which condition increases heart rate?
Options:
a. Parasympathetic stimulation
b. Increased vagal tone
c. Sympathetic stimulation
d. High end-systolic volume

Explanation: Correct answer is c. Sympathetic stimulation increases heart rate by releasing norepinephrine, enhancing pacemaker activity. Parasympathetic stimulation and high vagal tone reduce HR. High end-systolic volume does not directly increase HR. Sympathetic control ensures cardiac output meets metabolic demands during stress or exercise.

6. Single Correct Answer MCQ:
Ejection fraction is calculated as:
Options:
a. SV/EDV × 100
b. EDV/ESV × 100
c. CO/HR × 100
d. SV × HR

Explanation: Correct answer is a. Ejection fraction (EF) = Stroke volume/End-diastolic volume × 100, indicating ventricular pumping efficiency. Normal EF is 55–70%. It measures the fraction of filled blood ejected per beat, critical for assessing cardiac health, diagnosing heart failure, and evaluating therapeutic interventions in cardiovascular medicine.

7. Assertion-Reason MCQ:
Assertion (A): Cardiac output increases during exercise.
Reason (R): Both stroke volume and heart rate increase during exercise.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. During exercise, sympathetic stimulation increases heart rate and stroke volume, raising cardiac output. Enhanced venous return and myocardial contractility contribute. This coordinated response ensures adequate oxygen delivery to muscles and tissues, illustrating the physiological mechanism linking cardiac performance to metabolic demands during physical activity.

8. Matching Type MCQ:
Match the terms with definitions:
Column-I Column-II
(a) EDV (i) Blood volume remaining after systole
(b) ESV (ii) Volume pumped per beat
(c) SV (iii) Volume in ventricle at diastole end
(d) CO (iv) Blood pumped per minute
Options:
1. a-iii, b-i, c-ii, d-iv
2. a-ii, b-iii, c-i, d-iv
3. a-iv, b-ii, c-i, d-iii
4. a-i, b-ii, c-iii, d-iv

Explanation: Correct answer is 1. EDV is ventricle volume at diastole end, ESV is volume remaining after systole, SV is the volume pumped per beat, and CO is blood pumped per minute. These definitions are fundamental for understanding cardiac function, efficiency, and hemodynamic calculations in cardiovascular physiology.

9. Fill in the Blanks / Completion MCQ:
Heart rate can be calculated using the formula: ________ / SV.
Options:
a. EDV
b. ESV
c. CO
d. Preload

Explanation: Correct answer is c. Heart rate = Cardiac output / Stroke volume. This formula demonstrates the interrelation of cardiac parameters, allowing calculation of beats per minute from CO and SV. It is essential in assessing cardiovascular performance, monitoring patient status, and diagnosing heart conditions efficiently.

10. Choose the correct statements MCQ:
Select the correct statements:
i. CO = SV × HR
ii. Stroke volume decreases with increased preload
iii. Sympathetic stimulation increases heart rate
iv. EDV < ESV
Options:
a. i and iii
b. ii and iv
c. i and iv
d. ii and iii

Explanation: Correct answer is a. Cardiac output equals stroke volume multiplied by heart rate. Sympathetic stimulation enhances HR and contractility. Stroke volume increases with preload, and EDV is always greater than ESV. These principles define normal cardiac mechanics, regulation, and adaptation to physiological demands, ensuring efficient circulation.

Topic: Circulatory System

Subtopic: Heart Valves and Blood Flow

Keyword Definitions:

• Tricuspid valve: Valve between right atrium and right ventricle, prevents backflow of blood.

• Bicuspid (Mitral) valve: Valve between left atrium and left ventricle, prevents backflow.

• Semilunar valve: Valves between ventricles and major arteries (aortic and pulmonary) preventing backflow.

• Right atrium: Heart chamber receiving deoxygenated blood from body.

• Left atrium: Heart chamber receiving oxygenated blood from lungs.

• Pulmonary artery: Carries deoxygenated blood from right ventricle to lungs.

Lead Question - 2018

Match the items given in Column – I with those in Column – II and select the correct option given below :

Column - I | Column – II

a. Tricuspid valve | i. Between left atrium and left ventricle

b. Bicuspid valve | ii. Between right ventricle and pulmonary artery

c. Semilunar valve | iii. Between right atrium and right ventricle

(A) a – ii , b – i, c – iii

(B) a – iii , b – i, c - ii

(C) a – i , b – ii, c – iii

(D) a – i , b – iii, c – ii

Explanation:

Answer is (B). The tricuspid valve is located between the right atrium and right ventricle, preventing backflow. The bicuspid (mitral) valve lies between the left atrium and left ventricle. Semilunar valves, including pulmonary and aortic valves, are located at the exit of ventricles to major arteries, preventing backflow.

Guessed NEET UG MCQs:

1) Single Correct: The valve between left ventricle and aorta is:

(A) Tricuspid

(B) Bicuspid

(C) Aortic semilunar

(D) Pulmonary semilunar

Explanation:

Answer is (C). The aortic semilunar valve prevents blood from flowing back into the left ventricle after ventricular contraction, ensuring unidirectional blood flow.

2) Single Correct: Which valve prevents backflow from pulmonary artery into right ventricle?

(A) Tricuspid

(B) Bicuspid

(C) Pulmonary semilunar

(D) Aortic semilunar

Explanation:

Answer is (C). The pulmonary semilunar valve at the exit of right ventricle prevents blood from returning, maintaining forward pulmonary circulation.

3) Single Correct: Heart sound “lub” is produced by closure of:

(A) Semilunar valves

(B) AV valves

(C) Pulmonary valve only

(D) Aortic valve only

Explanation:

Answer is (B). The first heart sound “lub” occurs due to closure of atrioventricular valves (tricuspid and mitral) during ventricular contraction.

4) Assertion-Reason:

Assertion: The bicuspid valve is also called mitral valve.

Reason: It has two cusps and is located between left atrium and ventricle.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). The bicuspid valve has two cusps, located between left atrium and ventricle, functioning to prevent backflow, which makes the reason correct.

5) Single Correct: Which valve has three cusps and prevents backflow into right ventricle?

(A) Tricuspid

(B) Pulmonary semilunar

(C) Bicuspid

(D) Mitral

Explanation:

Answer is (B). The pulmonary semilunar valve has three cusps and prevents backflow of blood into the right ventricle during diastole.

6) Single Correct: Which valve prevents backflow into left atrium during ventricular contraction?

(A) Tricuspid

(B) Bicuspid

(C) Pulmonary semilunar

(D) Aortic semilunar

Explanation:

Answer is (B). The bicuspid (mitral) valve prevents blood from regurgitating into the left atrium during left ventricular systole.

7) Matching Type:

Column I | Column II

a. Tricuspid | i. Right AV valve

b. Bicuspid | ii. Left AV valve

c. Pulmonary semilunar | iii. Right ventricular outflow valve

(A) a-i, b-ii, c-iii

(B) a-ii, b-i, c-iii

(C) a-iii, b-i, c-ii

(D) a-i, b-iii, c-ii

Explanation:

Answer is (A). Tricuspid is right AV valve, bicuspid is left AV valve, and pulmonary semilunar is right ventricular outflow valve, maintaining directional blood flow.

8) Fill in the Blank:

The valve located between left atrium and left ventricle is ______.

(A) Tricuspid

(B) Bicuspid

(C) Pulmonary semilunar

(D) Aortic semilunar

Explanation:

Answer is (B). The bicuspid valve, also known as mitral valve, is located between left atrium and ventricle and prevents backflow of oxygenated blood during contraction.

9) Choose the correct statements:

(i) Tricuspid valve has three cusps.

(ii) Mitral valve has two cusps.

(iii) Semilunar valves prevent backflow into atria.

(A) i and ii only

(B) i and iii only

(C) ii and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Tricuspid has three cusps, bicuspid has two. Semilunar valves prevent backflow into ventricles, not atria, making statement iii incorrect.

10) Clinical-type: A patient shows regurgitation into left atrium, diagnosed via echocardiography. Which valve is affected?

(A) Tricuspid

(B) Mitral (Bicuspid)

(C) Pulmonary semilunar

(D) Aortic semilunar

Explanation:

Answer is (B). Regurgitation into the left atrium occurs due to mitral valve incompetence, leading to backflow during systole, detected clinically and via echocardiography.

Topic: Blood and Immunity

Subtopic: Plasma Proteins

Keyword Definitions:

• Fibrinogen: Plasma protein involved in blood clotting.

• Globulin: Plasma protein contributing to immune defense mechanisms.

• Albumin: Plasma protein maintaining osmotic balance and blood volume.

• Osmotic balance: The maintenance of fluid distribution between blood and tissues.

• Blood clotting: Process preventing excessive bleeding by forming a clot.

• Defence mechanism: Biological processes that protect the body from infections.

Lead Question - 2018

Match the items given in Column I with those in Column –II and select the correct option given below :

Column –I | Column –II

a. Fibrinogen | i. Osmotic balance

b. Globulin | ii. Blood clotting

c. Albumin | iii. Defence mechanism

(A) a – ii, b – iii , c – i

(B) a – iii, b – ii , c - i

(C) a – i, b – iii , c – ii

(D) a – i, b – ii , c – iii

Explanation:

Answer is (A). Fibrinogen (a) is involved in blood clotting (ii). Globulin (b) forms antibodies and is crucial for defense mechanisms (iii). Albumin (c) maintains osmotic balance in plasma (i). Proper plasma protein function is essential for hemostasis, immunity, and fluid regulation.

Guessed Questions for NEET UG:

1) Single Correct: Which plasma protein primarily maintains blood osmotic pressure?

(A) Fibrinogen

(B) Albumin

(C) Globulin

(D) Hemoglobin

Explanation:

Answer is (B). Albumin is the most abundant plasma protein and regulates osmotic pressure, ensuring fluid balance between blood and tissues. Deficiency can cause edema.

2) Single Correct: Which plasma protein is directly involved in coagulation?

(A) Globulin

(B) Albumin

(C) Fibrinogen

(D) Hemoglobin

Explanation:

Answer is (C). Fibrinogen is converted to fibrin during coagulation, forming a clot and preventing excessive bleeding.

3) Single Correct: Immunoglobulins are classified as:

(A) Albumins

(B) Globulins

(C) Fibrinogen

(D) Hemoglobin

Explanation:

Answer is (B). Globulins include immunoglobulins (antibodies) that protect the body against pathogens, playing a central role in the immune system.

4) Assertion-Reason:

Assertion: Albumin deficiency leads to edema.

Reason: Albumin maintains blood osmotic pressure.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). Albumin deficiency reduces plasma osmotic pressure, causing fluid leakage into tissues, resulting in edema. Both assertion and reason are correct.

5) Single Correct: Low fibrinogen levels in plasma may cause:

(A) Increased immunity

(B) Bleeding disorders

(C) Dehydration

(D) Anemia

Explanation:

Answer is (B). Fibrinogen is vital for clot formation. Low levels impair coagulation, leading to bleeding tendencies and delayed wound healing.

6) Single Correct: Major component of plasma protein that forms antibodies:

(A) Albumin

(B) Fibrinogen

(C) Globulin

(D) Hemoglobin

Explanation:

Answer is (C). Globulin includes immunoglobulins that serve as antibodies, providing specific defense against pathogens.

7) Matching Type:

Column I | Column II

a. Albumin | i. Blood clotting

b. Fibrinogen | ii. Osmotic balance

c. Globulin | iii. Immunity

(A) a-ii, b-i, c-iii

(B) a-i, b-ii, c-iii

(C) a-iii, b-i, c-ii

(D) a-ii, b-iii, c-i

Explanation:

Answer is (A). Albumin maintains osmotic balance, fibrinogen participates in blood clotting, and globulin contributes to immunity.

8) Fill in the Blank:

_________ is converted to fibrin during coagulation.

(A) Albumin

(B) Fibrinogen

(C) Globulin

(D) Prothrombin

Explanation:

Answer is (B). Fibrinogen, a plasma protein, is enzymatically converted to fibrin by thrombin, forming the structural basis of a blood clot.

9) Choose the correct statements:

(i) Globulins include antibodies.

(ii) Albumin maintains blood volume.

(iii) Fibrinogen is involved in immunity.

(A) i and ii only

(B) ii and iii only

(C) i and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Globulins function as antibodies (i), and albumin maintains osmotic balance and blood volume (ii). Fibrinogen is for clotting, not immunity (iii).

10) Clinical-type: A patient with liver disease shows reduced plasma proteins. Which problem is most likely?

(A) Impaired clotting

(B) Weak immunity

(C) Edema

(D) All of the above

Explanation:

Answer is (D). Liver synthesizes albumin, fibrinogen, and globulins. Deficiency leads to edema (low albumin), bleeding disorders (low fibrinogen), and weakened immunity (low globulin).

Subtopic: Endocrine Regulation of Blood Pressure

Keyword Definitions:

Blood Pressure: Force exerted by circulating blood on vessel walls.

Blood Volume: Total amount of blood in the circulatory system.

ADH (Antidiuretic Hormone): Hormone secreted by posterior pituitary to conserve water.

Renin: Enzyme from kidney that regulates blood pressure via RAAS.

Aldosterone: Hormone from adrenal cortex that increases sodium reabsorption.

Atrial Natriuretic Factor (ANF): Hormone released by atria in response to increased blood volume, reduces BP.

RAAS: Renin-Angiotensin-Aldosterone System regulating blood pressure and fluid balance.

Clinical Significance: Dysregulation of these hormones can cause hypertension, hypotension, or edema.

Homeostasis: Maintenance of stable internal conditions including blood pressure.

Kidney Function: Regulates electrolyte balance, volume, and hormone secretion.

Cardiovascular Response: Hormonal adjustments maintain circulation under stress or volume changes.

Lead Question - 2017

A decrease in blood pressure / volume will not cause the release of:

(A) ADH

(B) Renin

(C) Atrial Natriuretic Factor

(D) Aldosterone

Explanation: A decrease in blood pressure or volume stimulates ADH, Renin, and Aldosterone to conserve water and sodium. Atrial Natriuretic Factor (ANF) is released when atrial pressure rises; it lowers BP. Thus, decreased BP does not trigger ANF secretion. Correct answer: C.

1. MCQ - Single Correct Answer

ADH primarily acts on:

(a) Liver

(b) Kidneys

(c) Lungs

(d) Heart

Explanation: ADH acts on kidney collecting ducts to increase water reabsorption, maintaining blood volume and pressure. Liver, lungs, and heart are not direct targets. Proper ADH secretion prevents hypotension and dehydration. Correct answer: b.

2. MCQ - Single Correct Answer

Renin release is triggered by:

(a) High blood pressure

(b) Low blood pressure

(c) High blood volume

(d) High sodium intake

Explanation: Renin is secreted by juxtaglomerular cells when blood pressure drops. It initiates RAAS to increase angiotensin II and aldosterone, raising BP. High blood pressure, volume, or sodium inhibits renin. Correct answer: b.

3. MCQ - Single Correct Answer (Clinical)

Hyperaldosteronism may cause:

(a) Hypotension

(b) Hypertension

(c) Low sodium loss

(d) Dehydration

Explanation: Excess aldosterone increases sodium retention and water reabsorption, raising blood volume and causing hypertension. Hypotension occurs with aldosterone deficiency. Correct answer: b.

4. MCQ - Single Correct Answer

ANF is released from:

(a) Kidneys

(b) Adrenal cortex

(c) Cardiac atria

(d) Pituitary gland

Explanation: Atrial Natriuretic Factor is secreted by cardiac atria in response to increased blood volume. It promotes sodium excretion and reduces blood pressure. Kidneys, adrenal cortex, and pituitary are not sources. Correct answer: c.

5. MCQ - Single Correct Answer

Which hormone decreases blood pressure?

(a) ADH

(b) Aldosterone

(c) ANF

(d) Renin

Explanation: ANF lowers blood pressure by promoting sodium and water excretion. ADH, Aldosterone, and Renin work to raise blood pressure. Proper ANF release prevents volume overload and hypertension. Correct answer: c.

6. MCQ - Single Correct Answer (Clinical)

A patient with hypovolemia will have elevated levels of:

(a) ANF

(b) ADH

(c) Both a and b

(d) None

Explanation: In hypovolemia, blood volume is low. The body increases ADH to conserve water. ANF is not released as atrial stretch is reduced. Correct answer: b.

7. MCQ - Assertion-Reason

Assertion (A): ANF secretion increases with high blood volume.

Reason (R): ANF promotes sodium and water excretion.

(a) Both A and R true, R correct explanation

(b) Both A and R true, R not correct explanation

(c) A true, R false

(d) A false, R true

Explanation: ANF is released when atrial pressure rises, promoting sodium and water excretion to lower blood volume and pressure. Both assertion and reason are true, and the reason correctly explains the assertion. Correct answer: a.

8. MCQ - Matching Type

Match hormone with function:

1. ADH - (a) Sodium excretion

2. Renin - (b) Initiates RAAS

3. ANF - (c) Water reabsorption

4. Aldosterone - (d) Sodium retention

Options:

(A) 1-c, 2-b, 3-a, 4-d

(B) 1-b, 2-c, 3-d, 4-a

(C) 1-a, 2-b, 3-c, 4-d

(D) 1-d, 2-c, 3-b, 4-a

Explanation: ADH: water reabsorption; Renin: initiates RAAS; ANF: sodium excretion; Aldosterone: sodium retention. Correct matching: 1-c, 2-b, 3-a, 4-d. Answer: A.

9. MCQ - Fill in the Blanks

_________ increases sodium and water reabsorption to raise blood pressure.

(a) ANF

(b) Aldosterone

(c) ADH

(d) Renin

Explanation: Aldosterone from adrenal cortex promotes sodium and water retention in kidneys, increasing blood volume and pressure. ANF reduces BP, ADH only conserves water, and renin indirectly raises BP via RAAS. Correct answer: b.

10. MCQ - Choose Correct Statements

Select correct statements about blood pressure regulation:

1. Decreased BP stimulates ADH release

2. ANF is released during low blood volume

3. Renin increases BP via RAAS

4. Aldosterone promotes sodium retention

Options:

(A) 1, 3, and 4

(B) 1 and 2

(C) 2 and 4

(D) All 1,2,3,4

Explanation: Low BP triggers ADH and renin release; aldosterone promotes sodium retention. ANF is secreted when blood volume is high, not low. Correct statements: 1, 3, and 4. Answer: A. 

Subtopic: Hepatic Portal System

Keyword Definitions:

• Hepatic Portal Vein – Vein carrying nutrient-rich blood from gastrointestinal organs to liver.

• Liver – Organ responsible for metabolism, detoxification, and bile secretion.

• Intestine – Absorptive organ where digested nutrients enter blood.

• Stomach – Organ of protein digestion and food storage.

• Kidneys – Organs of excretion and osmoregulation.

• Detoxification – Process of neutralizing harmful substances.

• Cirrhosis – Chronic liver disease with fibrosis.

• Portal Hypertension – Increased blood pressure in hepatic portal circulation.

• Hepatocytes – Functional liver cells performing metabolism.

• Bile – Secretion aiding fat emulsification and absorption.

• Clinical Hepatology – Study of liver disorders and treatment.

Lead Question – 2017:

The hepatic portal vein drains blood to liver from:

(A) Intestine

(B) Heart

(C) Stomach

(D) Kidneys

Explanation:

Correct answer is A (Intestine). The hepatic portal vein carries blood rich in absorbed nutrients from small intestine, stomach, pancreas, and spleen to the liver. This blood undergoes detoxification and nutrient metabolism before entering systemic circulation, ensuring toxins do not reach the body directly. (Answer: A)

1) Single Correct Answer MCQ:

Which organ receives the first supply of absorbed nutrients from the intestine?

(A) Heart

(B) Liver

(C) Kidney

(D) Lungs

Explanation:

The liver is the first organ to receive absorbed nutrients via hepatic portal circulation. This allows nutrient storage, detoxification, and regulation of blood sugar before nutrients enter systemic circulation. (Answer: B)

2) Single Correct Answer MCQ:

Which blood vessel directly carries absorbed sugars and amino acids from intestine?

(A) Hepatic artery

(B) Hepatic portal vein

(C) Pulmonary vein

(D) Renal vein

Explanation:

Hepatic portal vein directly carries glucose, amino acids, and other absorbed nutrients from intestine to liver for processing, ensuring toxins are filtered before reaching systemic blood. (Answer: B)

3) Single Correct Answer MCQ:

Which of the following does not drain into hepatic portal circulation?

(A) Pancreas

(B) Spleen

(C) Kidneys

(D) Intestine

Explanation:

Kidneys do not drain into hepatic portal system. They directly release blood into systemic circulation via renal veins, while pancreas, spleen, and intestine drain into portal vein. (Answer: C)

4) Single Correct Answer MCQ:

A patient with liver cirrhosis develops enlarged veins in esophagus. This condition is due to:

(A) Portal Hypertension

(B) Anemia

(C) Hypoglycemia

(D) Thrombosis

Explanation:

Portal Hypertension occurs in cirrhosis, causing increased venous pressure. It leads to varices in esophagus and stomach, risk of bleeding, and ascites. (Answer: A)

5) Single Correct Answer MCQ:

Which type of blood does hepatic portal vein carry?

(A) Oxygen-rich

(B) Carbon dioxide-rich

(C) Nutrient-rich

(D) Deoxygenated only

Explanation:

Hepatic portal vein carries nutrient-rich blood, mainly glucose, amino acids, and vitamins from digestive organs. Although oxygen content is lower, its main role is nutrient transport to liver. (Answer: C)

6) Single Correct Answer MCQ:

Which vessel supplies oxygenated blood to the liver?

(A) Hepatic portal vein

(B) Hepatic artery

(C) Hepatic vein

(D) Inferior vena cava

Explanation:

Hepatic artery supplies oxygenated blood to the liver, while portal vein carries nutrient-rich blood. Both mix in sinusoids to nourish hepatocytes. (Answer: B)

7) Assertion-Reason MCQ:

Assertion (A): Hepatic portal vein ensures detoxification of absorbed substances.

Reason (R): Blood from intestine directly enters systemic circulation without liver involvement.

(A) Both A and R true, R explains A

(B) Both A and R true, R does not explain A

(C) A true, R false

(D) A false, R true

Explanation:

Assertion is true because hepatic portal vein ensures detoxification. Reason is false since intestinal blood first passes through liver before systemic circulation. (Answer: C)

8) Matching Type MCQ:

Match the structures with blood flow:

1. Intestine – (i) Nutrient absorption

2. Liver – (ii) Detoxification

3. Hepatic vein – (iii) Carries blood to inferior vena cava

Options:

(A) 1-i, 2-ii, 3-iii

(B) 1-ii, 2-iii, 3-i

(C) 1-iii, 2-i, 3-ii

(D) 1-i, 2-iii, 3-ii

Explanation:

Correct match is 1-i (intestine for absorption), 2-ii (liver for detoxification), 3-iii (hepatic vein to inferior vena cava). (Answer: A)

9) Fill in the Blanks MCQ:

The blood vessel carrying nutrient-rich blood from intestine to liver is called __________.

(A) Hepatic artery

(B) Hepatic vein

(C) Hepatic portal vein

(D) Inferior vena cava

Explanation:

The correct answer is Hepatic portal vein. It is a unique vessel connecting digestive organs to liver for detoxification and nutrient metabolism. (Answer: C)

10) Choose the correct statements MCQ:

1. Hepatic portal vein connects intestine and liver.

2. It carries oxygenated blood.

3. Liver receives blood from two sources.

4. Kidneys drain directly into hepatic portal vein.

Options:

(A) 1, 3

(B) 2, 4

(C) 1, 2

(D) 3, 4

Explanation:

Correct statements are 1 and 3. Hepatic portal vein connects intestine to liver. Liver receives blood from portal vein and hepatic artery. It does not carry highly oxygenated blood, and kidneys do not drain into it. (Answer: A)

Topic: Blood and Circulation

Subtopic: Erythrocyte Structure and Function

Keyword Definitions:

• RBC – Red blood cells, erythrocytes, specialized for oxygen transport.

• Enucleate – Lacking a nucleus.

• Somatic cells – Body cells excluding gametes.

• Oxygen transport – Carriage of O2 from lungs to tissues via hemoglobin.

• Metabolize – Biochemical processes producing energy and maintaining cell function.

• Hemoglobin – Oxygen-binding protein in RBCs.

• Reproduction – Cell division to generate new cells.

• Clinical relevance – Knowledge of RBC structure aids understanding of anemia, hypoxia, and blood disorders.

Lead Question – 2017:

Adult human RBCs are enucleate. Which of the following statements(s) is/are most appropriate explanation for this feature ?

(a) They do not need to reproduce

(b) They are somatic cells

(c) They do not metabolize

(d) All their internal space is available for oxygen transport

Options :

(A) (b) and (c)

(B) Only (d)

(C) Only (a)

(D) (a), (c) and (d)

Explanation:

Adult human RBCs lack nuclei to maximize internal space for oxygen transport via hemoglobin. They cannot reproduce and have limited metabolic activity but are somatic cells. This adaptation enhances oxygen-carrying efficiency. (Answer: D)

1) What is the primary function of RBCs?

(A) Transport oxygen

(B) Immunity

(C) Hormone secretion

(D) Blood clotting

Explanation:

RBCs carry oxygen using hemoglobin. They lack organelles for protein synthesis, focusing on efficient oxygen transport. Immune function, hormone secretion, and clotting are carried out by other blood components. (Answer: A)

2) RBCs are enucleate to:

(A) Increase oxygen capacity

(B) Replicate faster

(C) Store glucose

(D) Produce antibodies

Explanation:

Absence of a nucleus allows RBCs to store more hemoglobin and carry more oxygen. They cannot replicate or produce antibodies, highlighting their specialized transport role. (Answer: A)

3) Lifespan of human RBCs is approximately:

(A) 120 days

(B) 30 days

(C) 1 year

(D) 5 days

Explanation:

Human RBCs live about 120 days in circulation. Enucleation limits repair and replication, leading to predictable lifespan and clearance by spleen. This is crucial for maintaining healthy blood and oxygen delivery. (Answer: A)

4) Clinical relevance: Enucleate RBCs lead to:

(A) Anemia if defective

(B) Hypoxia in oxygen transport failure

(C) Efficient gas exchange

(D) All of the above

Explanation:

Enucleate RBCs optimize oxygen transport but can contribute to anemia or hypoxia if defective. Their specialized structure ensures efficient gas exchange, demonstrating clinical significance in blood disorders. (Answer: D)

5) Which component occupies most of RBC interior?

(A) Hemoglobin

(B) Mitochondria

(C) Nucleus

(D) Ribosomes

Explanation:

Hemoglobin occupies the majority of RBC volume, enabling maximal oxygen transport. Lack of nucleus and organelles ensures space efficiency. RBCs rely on anaerobic metabolism for energy. (Answer: A)

6) RBC metabolism is primarily:

(A) Anaerobic glycolysis

(B) Oxidative phosphorylation

(C) Photosynthesis

(D) Fermentation of proteins

Explanation:

RBCs rely on anaerobic glycolysis for ATP production since they lack mitochondria. This allows oxygen transport without consuming the oxygen they carry. (Answer: A)

7) Assertion-Reason type:

Assertion (A): Adult RBCs are enucleate.

Reason (R): Enucleation maximizes space for hemoglobin and oxygen transport.

(A) Both A and R true, R is correct explanation

(B) Both A and R true, R not correct explanation

(C) A true, R false

(D) A false, R true

Explanation:

Both assertion and reason are correct; enucleation increases internal volume for hemoglobin, enhancing oxygen transport efficiency, a key adaptation in adult human erythrocytes. (Answer: A)

8) Matching type:

Match:

(A) RBC – (i) Enucleate, oxygen carrier

(B) WBC – (ii) Nucleated, immunity

(C) Platelet – (iii) Enucleate, clotting

(D) Reticulocyte – (iv) Nucleated, immature RBC

Options:

(A) A-i, B-ii, C-iii, D-iv

(B) A-iv, B-i, C-ii, D-iii

(C) A-ii, B-iii, C-i, D-iv

(D) A-iii, B-ii, C-i, D-iv

Explanation:

Correct match: RBC – enucleate oxygen carrier, WBC – nucleated immunity, Platelet – enucleate clotting, Reticulocyte – nucleated immature RBC. This helps in understanding blood component functions and clinical relevance. (Answer: A)

9) Fill in the blanks:

Adult human RBCs lack a ________ to maximize space for oxygen.

(A) Nucleus

(B) Mitochondria

(C) Hemoglobin

(D) Cell membrane

Explanation:

Adult RBCs lack a nucleus to allow more internal space for hemoglobin, improving oxygen transport efficiency. Organelles are minimized to support their specialized role. (Answer: A)

10) Choose the correct statements:

1. RBCs are enucleate.

2. RBCs metabolize anaerobically.

3. RBCs reproduce in circulation.

4. RBC internal space is mainly for oxygen.

Options:

(A) 1, 2, 4 only

(B) 1, 3, 4 only

(C) 2, 3, 4 only

(D) All correct

Explanation:

Statements 1, 2, and 4 are correct; RBCs lack nucleus, rely on anaerobic glycolysis, and utilize internal space for oxygen. They do not reproduce in circulation. These features illustrate adaptation for efficient oxygen delivery. (Answer: A)

Topic: Blood Composition
Subtopic: Serum and Plasma Differences

Keyword Definitions:

• Serum: The liquid portion of blood after clotting, lacking clotting factors but containing antibodies, proteins, and electrolytes.

• Plasma: The liquid component of blood before clotting, containing clotting factors like fibrinogen.

• Clotting Factors: Proteins essential for blood coagulation, mainly fibrinogen.

• Antibodies: Proteins of immune system found in plasma and serum.

• Globulins: A group of proteins including antibodies, aiding immunity and transport.

• Albumin: Plasma protein maintaining osmotic balance and transport.

Lead Question - 2016 (Phase 2)
Serum differs from blood in :
(1) lacking antibodies
(2) lacking globulins
(3) lacking albumins
(4) lacking cloting factors

Explanation: Serum is blood plasma without clotting factors. It still contains antibodies, globulins, and albumin. Correct answer is (4) lacking clotting factors. This difference is clinically useful for biochemical tests as serum does not clot and allows stable analysis of proteins and metabolites.

1. Which protein is removed from plasma during clot formation, resulting in serum?
(1) Albumin
(2) Fibrinogen
(3) Globulin
(4) Immunoglobulin

Explanation: Fibrinogen is a clotting factor present in plasma but absent in serum because it is used up during clot formation. Correct answer is (2) Fibrinogen. Albumin, globulin, and immunoglobulins remain in serum after clotting occurs.

2. A patient’s serum sample is used instead of plasma in biochemical tests because:
(1) It contains clotting factors
(2) It is free from clotting factors
(3) It has no proteins
(4) It lacks electrolytes

Explanation: Serum is preferred for biochemical tests as it lacks clotting factors, making it stable and easier to handle. Correct answer is (2) It is free from clotting factors. Proteins and electrolytes are still present in serum, unlike option (3) or (4).

3. Which of the following is present in both plasma and serum?
(1) Fibrinogen
(2) Albumin
(3) Prothrombin
(4) Clotting factors

Explanation: Albumin is present in both plasma and serum, as it is not involved in clotting. Correct answer is (2) Albumin. Fibrinogen and prothrombin are consumed in clot formation and absent in serum, while clotting factors are missing from serum.

4. Assertion-Reason: Assertion: Serum is preferred for diagnostic tests. Reason: Serum lacks clotting factors, ensuring stable sample composition.
(1) Both A and R true, R explains A
(2) Both A and R true, R not explanation
(3) A true, R false
(4) A false, R true

Explanation: Serum lacks clotting factors, making it ideal for biochemical assays. Both assertion and reason are correct, and the reason explains assertion. Correct answer is (1) Both A and R true, R explains A. This is why clinical labs prefer serum samples for routine testing.

5. Which of the following is absent in serum but present in plasma?
(1) Antibodies
(2) Albumin
(3) Fibrinogen
(4) Electrolytes

Explanation: Fibrinogen, a clotting factor, is absent in serum as it is used up during clot formation. Correct answer is (3) Fibrinogen. Antibodies, albumin, and electrolytes remain present in both serum and plasma, making serum useful for diagnostic investigations.

6. A patient with suspected viral infection had serum tested for antibodies. Why serum?
(1) Antibodies remain after clotting
(2) Antibodies disappear after clotting
(3) Serum lacks proteins
(4) Serum prevents hemoglobin release

Explanation: Antibodies are proteins found in plasma and serum. They remain after clotting, hence serum is tested for antibody presence. Correct answer is (1) Antibodies remain after clotting. This makes serum useful in ELISA and immunological tests.

7. Matching Type: Match the component with its presence:
A. Fibrinogen
B. Albumin
C. Antibodies
D. Electrolytes
(i) Plasma only
(ii) Plasma and Serum
(iii) Plasma and Serum
(iv) Plasma and Serum
(1) A-i, B-ii, C-iii, D-iv
(2) A-ii, B-i, C-iv, D-iii
(3) A-i, B-iii, C-ii, D-iv
(4) A-i, B-iv, C-iii, D-ii

Explanation: Fibrinogen is found in plasma only, while albumin, antibodies, and electrolytes remain in both plasma and serum. Correct answer is (1) A-i, B-ii, C-iii, D-iv. Thus, serum and plasma differ mainly in clotting factor presence.

8. Fill in the Blank: Serum is blood plasma without __________.
(1) Glucose
(2) Clotting factors
(3) Antibodies
(4) Albumin

Explanation: Serum is blood plasma devoid of clotting factors but still contains proteins and antibodies. Correct answer is (2) Clotting factors. This absence makes serum a stable choice for biochemical and immunological investigations in clinical settings.

9. Which test is commonly done on serum rather than plasma?
(1) CBC
(2) Liver function test
(3) Coagulation test
(4) ESR

Explanation: Liver function tests are typically done using serum because serum is free of clotting factors and provides stable protein levels. Correct answer is (2) Liver function test. CBC and ESR require whole blood, while coagulation studies use plasma.

10. Choose the correct statements regarding serum:
(1) Serum is plasma without clotting factors
(2) Serum contains antibodies
(3) Serum contains fibrinogen
(4) Serum is used in biochemical tests
(A) 1, 2, 4 only
(B) 1 and 3 only
(C) 2 and 3 only
(D) All four

Explanation: Serum lacks clotting factors but retains antibodies and is widely used in biochemical testing. Fibrinogen is absent. Correct answer is (A) 1, 2, 4 only. Thus, serum remains essential in diagnostic pathology and clinical practice.

Topic: Blood Components

Subtopic: Platelets and Clotting Disorders

Keyword Definitions

• Thrombocytes: Also called platelets, responsible for blood clotting and wound healing.

• Erythrocytes: Red blood cells that transport oxygen and carbon dioxide.

• Leucocytes: White blood cells involved in immunity.

• Neutrophils: A type of white blood cell important in defense against infections.

• Hemostasis: The process of stopping bleeding through clot formation.

• Clotting factors: Proteins in blood plasma required for clot formation.

• Thrombocytopenia: A condition of low platelet count causing bleeding risk.

• Plasma: The fluid part of blood carrying cells and proteins.

• Hemophilia: Genetic disorder where clotting factors are deficient.

• Fibrin: Protein threads forming the framework of blood clots.

Lead Question - 2016 (Phase 2)

Name the blood cells, whose reduction in number can cause clotting disorder, leading to excessive loss of blood from the body :

(1) Thrombocytes
(2) Erythrocytes
(3) Leucocytes
(4) Neutrophils

Explanation: Thrombocytes (platelets) play a key role in clot formation. Their deficiency, known as thrombocytopenia, leads to bleeding disorders and excessive blood loss. Erythrocytes transport gases, while leucocytes and neutrophils help in immunity but not clotting. Hence, the correct answer is (1) Thrombocytes.

1. Which vitamin deficiency can worsen bleeding tendency in a patient with thrombocytopenia?

(1) Vitamin A
(2) Vitamin K
(3) Vitamin C
(4) Vitamin D

Explanation: Vitamin K is essential for the synthesis of clotting factors. Deficiency of vitamin K worsens bleeding disorders, especially in patients with low platelet counts. Other vitamins are important for general health but not directly for clotting. Correct answer is (2) Vitamin K.

2. A patient presents with pinpoint hemorrhages (petechiae). The most likely cause is:

(1) Leukopenia
(2) Thrombocytopenia
(3) Anemia
(4) Polycythemia

Explanation: Petechiae are tiny hemorrhages seen when platelet count is low (thrombocytopenia). Leukopenia affects immunity, anemia causes fatigue, and polycythemia increases blood viscosity but not pinpoint bleeding. Correct answer is (2) Thrombocytopenia.

3. Which of the following is released from platelets during clotting?

(1) Histamine
(2) Serotonin
(3) Acetylcholine
(4) Dopamine

Explanation: Platelets release serotonin, which causes vasoconstriction and reduces blood flow at the site of injury, aiding clotting. Histamine comes from mast cells, acetylcholine is a neurotransmitter, and dopamine acts in the CNS. Correct answer is (2) Serotonin.

4. A young child with repeated nosebleeds is diagnosed with hemophilia. Which factor is deficient?

(1) Factor IX
(2) Factor VII
(3) Factor XIII
(4) Factor XI

Explanation: Hemophilia A is due to deficiency of Factor VIII, while Hemophilia B involves Factor IX deficiency. Both cause prolonged bleeding. Among given choices, the closest is Factor IX deficiency (Hemophilia B). Correct answer is (1) Factor IX.

5. In dengue fever, low platelet count can cause:

(1) Stroke
(2) Severe bleeding
(3) Hypertension
(4) Diabetes

Explanation: Dengue fever often causes thrombocytopenia, leading to severe bleeding manifestations such as gum bleeding, nosebleeds, and internal hemorrhage. Stroke, hypertension, and diabetes are unrelated. Correct answer is (2) Severe bleeding.

6. Platelets are derived from which precursor cell?

(1) Megakaryocytes
(2) Monocytes
(3) Lymphocytes
(4) Basophils

Explanation: Platelets originate from megakaryocytes in the bone marrow. Monocytes, lymphocytes, and basophils are types of white blood cells. The cytoplasmic fragments of megakaryocytes form thrombocytes. Correct answer is (1) Megakaryocytes.

7. Assertion-Reason: Platelets are essential for clotting. Patients with low platelet count bleed excessively.

(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Platelets aggregate and release chemicals aiding clot formation. In thrombocytopenia, bleeding time increases. Thus, both assertion and reason are true, and reason correctly explains assertion. Correct answer is (1).

8. Match the following:

A. Platelets
B. Erythrocytes
C. Neutrophils
D. Plasma
(i) Oxygen transport
(ii) Clotting
(iii) Immunity
(iv) Nutrient transport

(1) A-ii, B-i, C-iii, D-iv
(2) A-i, B-ii, C-iii, D-iv
(3) A-iv, B-iii, C-i, D-ii
(4) A-iii, B-iv, C-ii, D-i

Explanation: Platelets help in clotting, erythrocytes transport oxygen, neutrophils are immune defenders, and plasma transports nutrients and hormones. Correct answer is (1) A-ii, B-i, C-iii, D-iv.

9. Fill in the blank: Platelet count below ______ per microliter is considered dangerous for spontaneous bleeding.

(1) 1,50,000
(2) 1,00,000
(3) 50,000
(4) 20,000

Explanation: A platelet count below 20,000 per microliter is very dangerous and can cause spontaneous internal bleeding. Mild thrombocytopenia occurs above this but is less critical. Correct answer is (4) 20,000.

10. Choose the correct statements regarding platelets:

(1) Platelets live for about 120 days
(2) They are fragments of megakaryocytes
(3) They release factors aiding clotting
(4) Platelet count is normally 1.5–4.5 lakhs/μL

(1) 1,2 correct
(2) 2,3,4 correct
(3) 1,4 correct
(4) All correct

Explanation: Platelets survive only 7–10 days, not 120. They are fragments of megakaryocytes, release clotting chemicals, and their count is 1.5–4.5 lakhs/μL. Correct answer is (2) 2,3,4 correct.

Topic: Circulatory System

Subtopic: Pulmonary Circulation

Keyword Definitions:

• Pulmonary Artery: Blood vessel carrying deoxygenated blood from right ventricle to lungs.

• Aorta: Largest artery carrying oxygenated blood from left ventricle to the body.

• Carotid Artery: Major artery supplying oxygenated blood to the brain.

• Pulmonary Vein: Vessel carrying oxygenated blood from lungs to left atrium of heart.

• Venae Cavae: Large veins (superior and inferior) returning deoxygenated blood to the heart.

2016 (Phase 1)

Lead Question: Blood pressure in the pulmonary artery is :

• (1) Same as that in the aorta

• (2) More than that in the carotid

• (3) More than that in the pulmonary vein

• (4) Less than that in the venae cavae

Answer & Explanation: The correct answer is (3). Blood pressure in the pulmonary artery is higher than in the pulmonary vein but lower than in the systemic arteries like the aorta. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs at lower pressure to prevent damage to delicate lung capillaries.

Keyword Definitions:

• Pulmonary Circulation: Circulation of blood between heart and lungs for gas exchange.

2021

Single Correct Answer MCQ: The primary function of pulmonary circulation is to:

• (1) Supply oxygenated blood to body tissues

• (2) Remove metabolic waste from tissues

• (3) Facilitate gas exchange between blood and lungs

• (4) Transport nutrients from the digestive system

Answer & Explanation: The correct answer is (3). Pulmonary circulation carries deoxygenated blood from the right ventricle to the lungs, where carbon dioxide is exchanged for oxygen. Oxygenated blood returns to the left atrium to be pumped into systemic circulation, essential for maintaining proper body function.

Keyword Definitions:

• Gas Exchange: Process where oxygen enters and carbon dioxide leaves blood in the lungs.

2019

Single Correct Answer MCQ (Clinical Type): In pulmonary hypertension, blood pressure in the pulmonary artery is:

• (1) Decreased

• (2) Unchanged

• (3) Increased

• (4) Variable

Answer & Explanation: The correct answer is (3). Pulmonary hypertension is a clinical condition where pulmonary artery pressure increases, leading to strain on the right ventricle and possible heart failure. Causes include chronic lung disease, left heart disease, or idiopathic factors, requiring medical intervention.

Keyword Definitions:

• Pulmonary Hypertension: Increased pressure in pulmonary arteries, leading to cardiovascular complications.

2018

Single Correct Answer MCQ: What prevents backflow of blood from pulmonary artery into the right ventricle?

• (1) Pulmonary Semilunar Valve

• (2) Tricuspid Valve

• (3) Bicuspid Valve

• (4) Aortic Valve

Answer & Explanation: The correct answer is (1). The pulmonary semilunar valve prevents backflow of blood into the right ventricle during diastole, ensuring one-way blood flow from the heart to the lungs for oxygenation. Proper valve function is critical for effective circulation and preventing heart failure.

Keyword Definitions:

• Semilunar Valve: Valve located between heart chambers and arteries preventing backflow.

2017

Assertion-Reason MCQ:

Assertion (A): Pulmonary artery carries deoxygenated blood.

Reason (R): Pulmonary artery connects right ventricle to lungs for gas exchange.

• (1) Both A and R are true, and R is the correct explanation of A.

• (2) Both A and R are true, but R is not the correct explanation of A.

• (3) A is true, but R is false.

• (4) A is false, but R is true.

Answer & Explanation: The correct answer is (1). The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs for oxygenation. Unlike systemic arteries, which carry oxygenated blood, the pulmonary artery is unique in transporting low-oxygen blood to the lungs for gas exchange.

Keyword Definitions:

• Gas Exchange: The process where CO2 is released and O2 is absorbed in lungs.

2016

Matching Type MCQ: Match the vessel with the correct pressure status:

A. Pulmonary Artery       1. Low Pressure

B. Aorta                  2. High Pressure

C. Venae Cavae            3. Very Low Pressure

• (1) A-1, B-2, C-3

• (2) A-2, B-1, C-3

• (3) A-3, B-2, C-1

• (4) A-1, B-3, C-2

Answer & Explanation: The correct answer is (1). Pulmonary artery carries blood at lower pressure compared to systemic arteries due to shorter distance and fragile lungs. The aorta carries high-pressure oxygenated blood, and venae cavae have very low pressure returning blood to the heart.

Keyword Definitions:

• Systemic Circulation: Circulation of oxygenated blood from heart to body and back.

2015

Fill in the Blanks MCQ: The normal pulmonary arterial pressure is approximately __________ mmHg.

• (1) 120/80

• (2) 25/10

• (3) 90/60

• (4) 140/90

Answer & Explanation: The correct answer is (2). Normal pulmonary arterial pressure is around 25 mmHg systolic and 10 mmHg diastolic. Elevated pressures indicate pulmonary hypertension, which can cause right heart strain and clinical complications requiring medical attention.

Keyword Definitions:

• Pulmonary Arterial Pressure: Pressure of blood in pulmonary artery, normally 25/10 mmHg.

2022

Choose the correct statements MCQ:

• 1. Pulmonary artery carries deoxygenated blood.

• 2. Pulmonary vein carries deoxygenated blood.

• 3. Pulmonary artery pressure is lower than aortic pressure.

• 4. Venae cavae have lower pressure than pulmonary artery.

• (1) 1, 3, 4 only

• (2) 1 and 2 only

• (3) 2 and 3 only

• (4) All statements are correct

Answer & Explanation: The correct answer is (1). Pulmonary artery carries deoxygenated blood, while pulmonary vein carries oxygenated blood. Pulmonary artery pressure is lower than systemic arteries, and venae cavae have very low pressure returning blood to the heart. This ensures efficient pulmonary circulation without damaging lung tissues.

Topic: Acid-Base Balance in Blood

Subtopic: pH Regulation and Hemoglobin Function

• pH: A measure of hydrogen ion concentration in a solution, indicating its acidity or alkalinity.

• Hemoglobin Affinity: The ability of hemoglobin to bind oxygen, affected by pH and other factors.

• Bohr Effect: Decreased pH lowers hemoglobin’s affinity for oxygen, facilitating oxygen release to tissues.

• Bicarbonate Buffer System: Maintains blood pH by balancing carbonic acid and bicarbonate ions.

• Acidosis: Condition where blood pH drops below normal (7.35), impairing physiological functions.

Lead Question - 2016 (Phase 1)

Reduction in pH of blood will :

• (1) reduce the rate of heartbeat.

• (2) reduce the blood supply to the brain.

• (3) decrease the affinity of hemoglobin with oxygen.

• (4) release bicarbonate ions by the liver.

Answer & Explanation: (3) decrease the affinity of hemoglobin with oxygen. Reduced blood pH causes the Bohr effect, where hemoglobin releases oxygen more readily to tissues. This enhances oxygen delivery under acidic conditions caused by high metabolic activity, critical in maintaining tissue oxygenation during acidosis or intense exercise.

MCQ 1 (Single Correct Answer)

What is the Bohr effect?

• (A) Increased pH increases hemoglobin’s oxygen affinity

• (B) Decreased pH decreases hemoglobin’s oxygen affinity

• (C) Increased pH decreases oxygen release

• (D) pH does not affect hemoglobin function

Answer & Explanation: (B) Decreased pH decreases hemoglobin’s oxygen affinity. The Bohr effect explains how lower pH (increased H+ concentration) reduces hemoglobin’s affinity for oxygen, promoting oxygen release to metabolically active tissues, especially important during exercise or pathological acidosis.

MCQ 2 (Single Correct Answer)

What happens when blood pH falls significantly below normal?

• (A) Increased oxygen transport

• (B) Respiratory acidosis

• (C) Alkalosis

• (D) Increased bicarbonate excretion by liver

Answer & Explanation: (B) Respiratory acidosis. Blood pH reduction leads to acidosis due to CO₂ accumulation, impairing enzyme function and oxygen transport. The body compensates via buffering systems and altered respiration to restore pH balance.

MCQ 3 (Single Correct Answer)

Which organ plays the primary role in pH regulation of blood?

• (A) Liver

• (B) Pancreas

• (C) Kidney

• (D) Heart

Answer & Explanation: (C) Kidney. The kidneys regulate blood pH by excreting hydrogen ions and reabsorbing bicarbonate, maintaining acid-base homeostasis, especially during metabolic acidosis or alkalosis.

MCQ 4 (Single Correct Answer)

Why does a low pH favor oxygen release from hemoglobin?

• (A) It stabilizes the oxygen-hemoglobin bond

• (B) It destabilizes the bond, releasing oxygen

• (C) It enhances oxygen binding

• (D) pH has no effect on binding

Answer & Explanation: (B) It destabilizes the bond, releasing oxygen. The Bohr effect describes how acidic conditions weaken hemoglobin-oxygen bonds, promoting oxygen release to active tissues with higher CO₂ and lower pH.

MCQ 5 (Single Correct Answer)

Clinical relevance of acidosis includes:

• (A) Increased oxygen affinity

• (B) Impaired oxygen delivery

• (C) Enhanced tissue oxygenation

• (D) Neutral effect on respiration

Answer & Explanation: (B) Impaired oxygen delivery. Severe acidosis reduces hemoglobin's oxygen-carrying efficiency, leading to hypoxia, confusion, and organ failure if untreated. Clinical management targets pH correction and underlying causes.

MCQ 6 (Single Correct Answer)

Which buffer system maintains blood pH?

• (A) Phosphate buffer system

• (B) Protein buffer system

• (C) Bicarbonate buffer system

• (D) Ammonium buffer system

Answer & Explanation: (C) Bicarbonate buffer system. It maintains blood pH by balancing carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃⁻), neutralizing excess acids or bases to keep pH within the narrow range (7.35–7.45).

MCQ 7 (Assertion-Reason)

Assertion (A): A decrease in blood pH reduces hemoglobin's oxygen affinity.

Reason (R): Increased H+ concentration stabilizes the deoxygenated form of hemoglobin.

• (A) Both A and R are true and R is correct explanation of A.

• (B) Both A and R are true, but R is not correct explanation of A.

• (C) A is true, but R is false.

• (D) A is false, but R is true.

Answer & Explanation: (A) Both A and R are true and R is correct explanation of A. Lower pH increases H+ binding to hemoglobin, stabilizing its deoxygenated form and reducing oxygen affinity, enhancing oxygen release to tissues during acidosis.

MCQ 8 (Matching Type)

Match Organ to Function:

• 1. Lungs

• 2. Kidneys

• 3. Liver

• 4. Heart

1. Excretes hydrogen ions to regulate pH

2. Oxygenates blood and expels CO₂

3. Detoxifies metabolic products and produces urea

4. Pumps oxygenated blood to tissues

• (A) 1-B, 2-A, 3-C, 4-D

• (B) 1-A, 2-B, 3-C, 4-D

• (C) 1-C, 2-D, 3-A, 4-B

• (D) 1-D, 2-A, 3-B, 4-C

Answer & Explanation: (A) 1-B, 2-A, 3-C, 4-D. The lungs oxygenate blood and expel CO₂. The kidneys regulate pH by excreting H+. The liver detoxifies metabolic products and produces urea. The heart pumps oxygenated blood to tissues.

MCQ 9 (Fill in the Blanks)

Reduction in blood pH causes ______ effect, decreasing hemoglobin’s ______ for oxygen.

• (A) Bohr, affinity

• (B) Pasteur, capacity

• (C) Bohr, production

• (D) None, reactivity

Answer & Explanation: (A) Bohr, affinity. The Bohr effect refers to decreased hemoglobin oxygen affinity at lower pH, promoting oxygen release to tissues with higher metabolic activity, essential for survival under acidic conditions.

MCQ 10 (Choose the Correct Statements)

Which of the following statements are correct?

• 1. Decreased pH enhances oxygen release by hemoglobin.

• 2. Bicarbonate ions are released by the liver to regulate pH.

• 3. Kidneys help in excreting hydrogen ions to maintain pH.

• 4. High pH reduces oxygen release from hemoglobin.

• (A) 1, 3, and 4 only

• (B) 1 and 3 only

• (C) 2 and 3 only

• (D) All statements are correct

Answer & Explanation: (B) 1 and 3 only. Decreased pH enhances oxygen release (Bohr effect) and kidneys excrete hydrogen ions to regulate pH. The liver does not release bicarbonate ions; they are regulated by the blood buffer system and kidneys. High pH increases hemoglobin’s affinity, not reduces it.